tasks a-s

Task/Same-Fringe/0DESCRIPTION

@@ -0,0 +1,5 @@
+Write a routine that will compare the leaves ("fringe") of two binary trees to determine whether they are the same list of leaves when visited left-to-right.  The structure or balance of the trees does not matter; only the number, order, and value of the leaves is important.
+
+Any solution is allowed here, but many computer scientists will consider it inelegant to collect either fringe in its entirety before starting to collect the other one.  In fact, this problem is usually proposed in various forums as a way to show off various forms of concurrency (tree-rotation algorithms have also been used to get around the need to collect one tree first).  Thinking of it a slightly different way, an elegant solution is one that can perform the minimum amount of work to falsify the equivalence of the fringes when they differ somewhere in the middle, short-circuiting the unnecessary additional traversals and comparisons.
+
+Any representation of a binary tree is allowed, as long as the nodes are orderable, and only downward links are used (for example, you may not use parent or sibling pointers to avoid recursion).

Task/Same-Fringe/Ada/same-fringe-1.ada

@@ -0,0 +1,26 @@
+generic
+   type Data is private;
+package Bin_Trees is
+
+   type Tree_Type is private;
+
+   function Empty(Tree: Tree_Type) return Boolean;
+   function Left (Tree: Tree_Type) return Tree_Type;
+   function Right(Tree: Tree_Type) return Tree_Type;
+   function Item (Tree: Tree_Type) return Data;
+   function Empty return Tree_Type;
+
+   procedure Destroy_Tree(N: in out Tree_Type);
+   function Tree(Value: Data) return Tree_Type;
+   function Tree(Value: Data; Left, Right : Tree_Type) return Tree_Type;
+
+private
+
+   type Node;
+   type Tree_Type is access Node;
+   type Node is record
+      Left, Right: Tree_Type := null;
+      Item: Data;
+   end record;
+
+end Bin_Trees;

Task/Same-Fringe/Ada/same-fringe-2.ada

@@ -0,0 +1,52 @@
+with Ada.Unchecked_Deallocation;
+
+package body Bin_Trees is
+
+   function Empty(Tree: Tree_Type) return Boolean is
+   begin
+      return Tree = null;
+   end Empty;
+
+   function Empty return Tree_Type is
+   begin
+      return null;
+   end Empty;
+
+   function Left (Tree: Tree_Type) return Tree_Type is
+   begin
+      return Tree.Left;
+   end Left;
+
+   function Right(Tree: Tree_Type) return Tree_Type is
+   begin
+      return Tree.Right;
+   end Right;
+
+   function Item (Tree: Tree_Type) return Data is
+   begin
+      return Tree.Item;
+   end Item;
+
+   procedure Destroy_Tree(N: in out Tree_Type) is
+      procedure free is new Ada.Unchecked_Deallocation(Node, Tree_Type);
+   begin
+      if not Empty(N) then
+         Destroy_Tree(N.Left);
+         Destroy_Tree(N.Right);
+         Free(N);
+      end if;
+   end Destroy_Tree;
+
+   function Tree(Value: Data; Left, Right : Tree_Type) return Tree_Type is
+      Temp : Tree_Type := new Node;
+   begin
+      Temp.all := (Left, Right, Value);
+      return Temp;
+   end Tree;
+
+   function Tree(Value: Data) return Tree_Type is
+   begin
+      return Tree(Value, null, null);
+   end Tree;
+
+end Bin_Trees;

Task/Same-Fringe/Ada/same-fringe-3.ada

@@ -0,0 +1,11 @@
+   generic
+      with procedure Process_Data(Item: Data);
+      with function Stop return Boolean;
+      with procedure Finish;
+   package Bin_Trees.Traverse is
+      task Inorder_Task is
+         entry Run(Tree: Tree_Type);
+         -- this will call each Item in Tree and, at the very end, it will call Finish
+         -- except when Stop becomes true; in this case, the task terminates
+      end Inorder_Task;
+   end Bin_Trees.Traverse;

Task/Same-Fringe/Ada/same-fringe-4.ada

@@ -0,0 +1,23 @@
+   package body Bin_Trees.Traverse is
+      task body Inorder_Task is
+         procedure Inorder(Tree: Tree_Type) is
+         begin
+            if not Empty(Tree) and not Stop then
+               Inorder(Tree.Left);
+               if not Stop then
+                  Process_Data(Item => Tree.Item);
+               end if;
+               if (not Stop) then
+                  Inorder(Tree.Right);
+               end if;
+            end if;
+         end Inorder;
+         T: Tree_Type;
+      begin
+         accept Run(Tree: Tree_Type) do
+            T := Tree;
+         end Run;
+         Inorder(T);
+         Finish;
+      end Inorder_Task;
+   end Bin_Trees.Traverse;

Task/Same-Fringe/Ada/same-fringe-5.ada

@@ -0,0 +1,162 @@
+with Ada.Text_IO, Bin_Trees.Traverse;
+
+procedure Main is
+
+   package B_Trees is new Bin_Trees(Character); use B_Trees;
+
+   function Same_Fringe(T1, T2: Tree_Type) return Boolean is
+
+      protected type Buffer_Type is
+         entry Write(Item: Character);
+         entry Write_Done;
+         entry Read_And_Compare(Item: Character);
+         entry Read_Done;
+         entry Wait_For_The_End;
+         function Early_Abort return Boolean;
+         function The_Same return Boolean;
+      private
+         Current: Character;
+         Readable: Boolean := False;
+         Done: Boolean := False;
+         Same: Boolean := True;
+         Finished: Boolean := False;
+      end Buffer_Type;
+
+      protected body Buffer_Type is
+
+         entry Write(Item: Character) when not Readable is
+         begin
+            Readable := True;
+            Current  := Item;
+         end Write;
+
+         entry Write_Done when not Readable is
+         begin
+            Readable := True;
+            Done     := True;
+         end Write_Done;
+
+         entry Read_And_Compare(Item: Character) when Readable is
+         begin
+            if Done then -- Producer is already out of items
+               Same := False;
+               Finished := True;
+               -- Readable remains True, else Consumer might lock itself out
+            elsif
+              Item /= Current then
+               Same := False;
+               Finished := True;
+               Readable := False;
+            else
+                 Readable := False;
+            end if;
+         end Read_And_Compare;
+
+         entry Read_Done when Readable is
+         begin
+            Readable := False;
+            Same     := Same and Done;
+            Finished := True;
+         end Read_Done;
+
+         entry Wait_For_The_End when (Finished) or (not Same) is
+         begin
+            null; -- "when ..." is all we need
+         end Wait_For_The_End;
+
+         function The_Same return Boolean is
+         begin
+            return Same;
+         end The_Same;
+
+         function Early_Abort return Boolean is
+         begin
+            return not The_Same or Finished;
+         end Early_Abort;
+
+      end Buffer_Type;
+
+      Buffer: Buffer_Type;
+
+      -- some wrapper subprogram needed to instantiate the generics below
+
+          procedure Prod_Write(Item: Character) is
+          begin
+             Buffer.Write(Item);
+          end Prod_Write;
+
+          function Stop return Boolean is
+          begin
+             return Buffer.Early_Abort;
+          end Stop;
+
+          procedure Prod_Stop is
+          begin
+             Buffer.Write_Done;
+          end Prod_Stop;
+
+          procedure Cons_Write(Item: Character) is
+          begin
+             Buffer.Read_And_Compare(Item);
+          end Cons_Write;
+
+          procedure Cons_Stop is
+          begin
+             Buffer.Read_Done;
+          end Cons_Stop;
+
+      package Producer is new B_Trees.Traverse(Prod_Write, Stop, Prod_Stop);
+      package Consumer is new B_Trees.Traverse(Cons_Write, Stop, Cons_Stop);
+
+   begin
+      Producer.Inorder_Task.Run(T1);
+      Consumer.Inorder_Task.Run(T2);
+      Buffer.Wait_For_The_End;
+      return Buffer.The_Same;
+   end Same_Fringe;
+
+   procedure Show_Preorder(Tree: Tree_Type; Prefix: String := "") is
+      use Ada.Text_IO;
+   begin
+      if Prefix /= "" then
+         Ada.Text_IO.Put(Prefix);
+      end if;
+      if not Empty(Tree) then
+         Put("(" & Item(Tree));      Put(", ");
+         Show_Preorder(Left(Tree));  Put(", ");
+         Show_Preorder(Right(Tree)); Put(")");
+      end if;
+      if Prefix /= "" then
+         New_Line;
+      end if;
+   end Show_Preorder;
+
+   T_0: Tree_Type := Tree('a', Empty, Tree('b'));
+   T: array(1 .. 5) of Tree_Type;
+
+begin
+   T(1) := Tree('d', Tree('c'), T_0);
+   T(2)  := Tree('c', Empty, Tree('a', Tree('d'), Tree('b')));
+   T(3)  := Tree('e', T(1), T(2));
+   T(4)  := Tree('e', T(2), T(1));
+   T(5)  := Tree('e', T_0, Tree('c', Tree('d'), T(1)));
+
+   -- First display the trees you have (in preorder)
+   for I in T'Range loop
+      Show_Preorder(T(I), "Tree(" & Integer'Image(I) & " ) is ");
+   end loop;
+   Ada.Text_IO.New_Line;
+
+   -- Now compare them, which have the same fringe?
+   for I in T'Range loop
+      for J in T'Range loop
+         if Same_Fringe(T(J), T(I)) then
+            Ada.Text_IO.Put("same(");
+         else
+            Ada.Text_IO.Put("DIFF(");
+         end if;
+         Ada.Text_IO.Put(Integer'Image(I) & "," & Integer'Image(J) & " ); ");
+      end loop;
+      Ada.Text_IO.New_Line;
+   end loop;
+end Main;

Task/Same-Fringe/C/same-fringe.c

@@ -0,0 +1,121 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <ucontext.h>
+
+typedef struct {
+	ucontext_t caller, callee;
+	char stack[8192];
+	void *in, *out;
+} co_t;
+
+co_t * co_new(void(*f)(), void *data)
+{
+	co_t * c = malloc(sizeof(*c));
+	getcontext(&c->callee);
+	c->in = data;
+
+	c->callee.uc_stack.ss_sp = c->stack;
+	c->callee.uc_stack.ss_size = sizeof(c->stack);
+	c->callee.uc_link = &c->caller;
+	makecontext(&c->callee, f, 1, (int)c);
+
+	return c;
+}
+
+void co_del(co_t *c)
+{
+	free(c);
+}
+
+inline void
+co_yield(co_t *c, void *data)
+{
+	c->out = data;
+	swapcontext(&c->callee, &c->caller);
+}
+
+inline void *
+co_collect(co_t *c)
+{
+	c->out = 0;
+	swapcontext(&c->caller, &c->callee);
+	return c->out;
+}
+
+// end of coroutine stuff
+
+typedef struct node node;
+struct node {
+	int v;
+	node *left, *right;
+};
+
+node *newnode(int v)
+{
+	node *n = malloc(sizeof(node));
+	n->left = n->right = 0;
+	n->v = v;
+	return n;
+}
+
+void tree_insert(node **root, node *n)
+{
+	while (*root) root = ((*root)->v > n->v)
+				? &(*root)->left
+				: &(*root)->right;
+	*root = n;
+}
+
+void tree_trav(int x)
+{
+	co_t *c = (co_t *) x;
+
+	void trav(node *root) {
+		if (!root) return;
+		trav(root->left);
+		co_yield(c, root);
+		trav(root->right);
+	}
+
+	trav(c->in);
+}
+
+int tree_eq(node *t1, node *t2)
+{
+	co_t *c1 = co_new(tree_trav, t1);
+	co_t *c2 = co_new(tree_trav, t2);
+
+	node *p = 0, *q = 0;
+	do {
+		p = co_collect(c1);
+		q = co_collect(c2);
+	} while (p && q && (p->v == q->v));
+
+	co_del(c1);
+	co_del(c2);
+	return !p && !q;
+}
+
+int main()
+{
+	int x[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1 };
+	int y[] = { 2, 5, 7, 1, 9, 0, 6, 4, 8, 3, -1 };
+	int z[] = { 0, 1, 2, 3, 4, 5, 6, 8, 9, -1 };
+
+	node *t1 = 0, *t2 = 0, *t3 = 0;
+
+	void mktree(int *buf, node **root) {
+		int i;
+		for (i = 0; buf[i] >= 0; i++)
+			tree_insert(root, newnode(buf[i]));
+	}
+
+	mktree(x, &t1); // ordered binary tree, result of traversing
+	mktree(y, &t2); // should be independent of insertion, so t1 == t2
+	mktree(z, &t3);
+
+	printf("t1 == t2: %s\n", tree_eq(t1, t2) ? "yes" : "no");
+	printf("t1 == t3: %s\n", tree_eq(t1, t3) ? "yes" : "no");
+
+	return 0;
+}

Task/Same-Fringe/D/same-fringe-1.d

@@ -0,0 +1,22 @@
+struct Node(T) {
+    T data;
+    Node* L, R;
+}
+
+bool sameFringe(T)(Node!T* t1, Node!T* t2) {
+    T[] scan(Node!T* t) {
+        if (!t) return [];
+        return (!t.L && !t.R) ? [t.data] : scan(t.L) ~ scan(t.R);
+    }
+    return scan(t1) == scan(t2);
+}
+
+void main() {
+    import std.stdio;
+    alias N = Node!int;
+    auto t1 = new N(10, new N(20, new N(30, new N(40), new N(50))));
+    auto t2 = new N(1, new N(2, new N(3, new N(40), new N(50))));
+    writeln(sameFringe(t1, t2));
+    auto t3 = new N(1, new N(2, new N(3, new N(40), new N(51))));
+    writeln(sameFringe(t1, t3));
+}

Task/Same-Fringe/D/same-fringe-2.d

@@ -0,0 +1,194 @@
+import std.array: empty;
+import std.algorithm: equal;
+
+
+// Replace with an efficient stack when available in Phobos.
+struct Stack(T) {
+    private T[] data;
+
+    public @property bool empty() const pure nothrow {
+        return data.empty;
+    }
+
+    // Can't be const if T isn't a value or const.
+    public @property T head() const pure nothrow
+    in {
+        assert(!data.empty);
+    } body {
+        return data[$ - 1];
+    }
+
+    public void push(T x) pure nothrow {
+        data ~= x;
+    }
+
+    public void pop() pure nothrow
+    in {
+        assert(!data.empty);
+    } body {
+        data.length--;
+    }
+}
+
+
+struct BinaryTreeNode(T) {
+    T data;
+    BinaryTreeNode* left, right;
+}
+
+
+struct Fringe(T) {
+    alias const(BinaryTreeNode!T)* BT;
+    private Stack!BT stack;
+
+    pure nothrow invariant() {
+        assert(stack.empty || isLeaf(stack.head));
+    }
+
+    public this(BT t) pure nothrow {
+        if (t != null) {
+            stack.push(t);
+            if (!isLeaf(t)) {
+                // Here invariant() doesn't hold.
+                // invariant() isn't called for private methods.
+                nextLeaf();
+            }
+        }
+    }
+
+    public @property bool empty() const pure nothrow {
+        return stack.empty;
+    }
+
+    public @property T front() const pure nothrow
+    in {
+        assert(!stack.empty && stack.head != null);
+    } body {
+        return stack.head.data;
+    }
+
+    public void popFront() pure nothrow
+    in {
+        assert(!stack.empty);
+    } body {
+        stack.pop();
+        if (!empty())
+            nextLeaf();
+    }
+
+    private static bool isLeaf(in BT t) pure nothrow {
+        return t != null && t.left == null && t.right == null;
+    }
+
+    private void nextLeaf() pure nothrow
+    in {
+        assert(!stack.empty);
+    } body {
+        auto t = stack.head;
+
+        while (!stack.empty && !isLeaf(t)) {
+            stack.pop();
+            if (t.right != null)
+                stack.push(t.right);
+            if (t.left != null)
+                stack.push(t.left);
+            t = stack.head;
+        }
+    }
+}
+
+
+bool sameFringe(T)(in BinaryTreeNode!T* t1, in BinaryTreeNode!T* t2)
+pure nothrow {
+    return Fringe!T(t1).equal(Fringe!T(t2));
+}
+
+
+unittest {
+    alias BinaryTreeNode!int N;
+
+    static N* n(in int x, N* l=null, N* r=null) pure nothrow {
+        return new N(x, l, r);
+    }
+
+    {
+        N* t;
+        assert(sameFringe(t, t));
+    }
+
+    {
+        const t1 = n(10);
+        const t2 = n(10);
+        assert(sameFringe(t1, t2));
+    }
+
+    {
+        const t1 = n(10);
+        const t2 = n(20);
+        assert(!sameFringe(t1, t2));
+    }
+
+    {
+        const t1 = n(10, n(20));
+        const t2 = n(30, n(20));
+        assert(sameFringe(t1, t2));
+    }
+
+    {
+        const t1 = n(10, n(20));
+        const t2 = n(10, n(30));
+        assert(!sameFringe(t1, t2));
+    }
+
+    {
+        const t1 = n(10, n(20), n(30));
+        const t2 = n(5, n(20), n(30));
+        assert(sameFringe(t1, t2));
+    }
+
+    {
+        const t1 = n(10, n(20), n(30));
+        const t2 = n(5, n(20), n(35));
+        assert(!sameFringe(t1, t2));
+    }
+
+    {
+        const t1 = n(10, n(20, n(30)));
+        const t2 = n(1, n(2, n(30)));
+        assert(sameFringe(t1, t2));
+    }
+
+    {
+        const t1 = n(10, n(20, n(30, n(40), n(50))));
+        const t2 = n(1, n(2, n(3, n(40), n(50))));
+        assert(sameFringe(t1, t2));
+    }
+
+    {
+        const t1 = n(10, n(20, n(30, n(40), n(50))));
+        const t2 = n(1, n(2, n(3, n(40), n(51))));
+        assert(!sameFringe(t1, t2));
+    }
+}
+
+
+void main() {
+    import std.stdio;
+    alias N = BinaryTreeNode!int;
+
+    static N* n(in int x, N* l=null, N* r=null) pure nothrow {
+        return new N(x, l, r);
+    }
+
+    const t1 = n(10, n(20, n(30, n(40), n(50))));
+    writeln("fringe(t1): ", Fringe!int(t1));
+
+    const t2 = n(1, n(2, n(3, n(40), n(50))));
+    writeln("fringe(t2): ", Fringe!int(t2));
+
+    const t3 = n(1, n(2, n(3, n(40), n(51))));
+    writeln("fringe(t3): ", Fringe!int(t3));
+
+    writeln("sameFringe(t1, t2): ", sameFringe(t1, t2));
+    writeln("sameFringe(t1, t3): ", sameFringe(t1, t3));
+}

Task/Same-Fringe/Go/same-fringe.go

@@ -0,0 +1,71 @@
+package main
+
+import "fmt"
+
+type node struct {
+    int
+    left, right *node
+}
+
+// function returns a channel that yields the leaves of the tree.
+// the channel is closed after all leaves are received.
+func leaves(t *node) chan int {
+    ch := make(chan int)
+    // recursive function to walk tree.
+    var f func(*node)
+    f = func(n *node) {
+        if n == nil {
+            return
+        }
+        // leaves are identified by having no children.
+        if n.left == nil && n.right == nil {
+            ch <- n.int
+        } else {
+            f(n.left)
+            f(n.right)
+        }
+    }
+    // goroutine runs concurrently with others.
+    // it walks the tree then closes the channel.
+    go func() {
+        f(t)
+        close(ch)
+    }()
+    return ch
+}
+
+func sameFringe(t1, t2 *node) bool {
+    f1 := leaves(t1)
+    f2 := leaves(t2)
+    for l1 := range f1 {
+        // both trees must yield a leaf, and the leaves must be equal.
+        if l2, ok := <-f2; !ok || l1 != l2 {
+            return false
+        }
+    }
+    // there must be nothing left in f2 after consuming all of f1.
+    _, ok := <-f2
+    return !ok
+}
+
+func main() {
+    // the different shapes of the trees is shown with indention.
+    // the leaves are easy to spot by the int: key.
+    t1 := &node{3,
+        &node{1,
+            &node{int: 1},
+            &node{int: 2}},
+        &node{8,
+            &node{int: 5},
+            &node{int: 13}}}
+    // t2 with negative values for internal nodes that can't possibly match
+    // positive values in t1, just to show that only leaves are being compared.
+    t2 := &node{-8,
+        &node{-3,
+            &node{-1,
+                &node{int: 1},
+                &node{int: 2}},
+            &node{int: 5}},
+        &node{int: 13}}
+    fmt.Println(sameFringe(t1, t2)) // prints true.
+}

Task/Same-Fringe/Haskell/same-fringe.hs

@@ -0,0 +1,24 @@
+data Tree a = Leaf a | Node (Tree a) (Tree a)
+    deriving (Show, Eq)
+
+fringe :: Tree a -> [a]
+fringe (Leaf x) = [x]
+fringe (Node n1 n2) = fringe n1 ++ fringe n2
+
+sameFringe :: (Eq a) => Tree a -> Tree a -> Bool
+sameFringe t1 t2 = fringe t1 == fringe t2
+
+main = do
+    let a = Node (Leaf 1) (Node (Leaf 2) (Node (Leaf 3) (Node (Leaf 4) (Leaf 5))))
+        b = Node (Leaf 1) (Node (Node (Leaf 2) (Leaf 3)) (Node (Leaf 4) (Leaf 5)))
+        c = Node (Node (Node (Node (Leaf 1) (Leaf 2)) (Leaf 3)) (Leaf 4)) (Leaf 5)
+    print $ sameFringe a a
+    print $ sameFringe a b
+    print $ sameFringe a c
+
+    let x = Node (Leaf 1) (Node (Leaf 2) (Node (Leaf 3) (Node (Leaf 4) (Node (Leaf 5) (Leaf 6)))))
+        y = Node (Leaf 0) (Node (Node (Leaf 2) (Leaf 3)) (Node (Leaf 4) (Leaf 5)))
+        z = Node (Leaf 1) (Node (Leaf 2) (Node (Node (Leaf 4) (Leaf 3)) (Leaf 5)))
+    print $ sameFringe a x
+    print $ sameFringe a y
+    print $ sameFringe a z

Task/Same-Fringe/J/same-fringe-1.j

@@ -0,0 +1 @@
+sameFringe=: -:&([: ; <S:0)

Task/Same-Fringe/J/same-fringe-2.j

@@ -0,0 +1 @@
+list2tree=: (<.@-:@# ({. ,&<&list2tree}. ) ])^:(1<#)

Task/Same-Fringe/J/same-fringe-3.j

@@ -0,0 +1,2 @@
+bp=: list2tree p: i.11
+ubp=: p:L:0] 10;~list2tree i.10

Task/Same-Fringe/J/same-fringe-4.j

@@ -0,0 +1,4 @@
+   ubp sameFringe bp
+1
+   bp sameFringe 1 {:: ubp
+0

Task/Same-Fringe/Java/same-fringe.java

@@ -0,0 +1,121 @@
+import java.util.*;
+
+class SameFringe
+{
+  public interface Node<T extends Comparable<? super T>>
+  {
+    Node<T> getLeft();
+    Node<T> getRight();
+    boolean isLeaf();
+    T getData();
+  }
+
+  public static class SimpleNode<T extends Comparable<? super T>> implements Node<T>
+  {
+    private final T data;
+    public SimpleNode<T> left;
+    public SimpleNode<T> right;
+
+    public SimpleNode(T data)
+    {  this(data, null, null);  }
+
+    public SimpleNode(T data, SimpleNode<T> left, SimpleNode<T> right)
+    {
+      this.data = data;
+      this.left = left;
+      this.right = right;
+    }
+
+    public Node<T> getLeft()
+    {  return left;  }
+
+    public Node<T> getRight()
+    {  return right;  }
+
+    public boolean isLeaf()
+    {  return ((left == null) && (right == null));  }
+
+    public T getData()
+    {  return data;  }
+
+    public SimpleNode<T> addToTree(T data)
+    {
+      int cmp = data.compareTo(this.data);
+      if (cmp == 0)
+        throw new IllegalArgumentException("Same data!");
+      if (cmp < 0)
+      {
+        if (left == null)
+          return (left = new SimpleNode<T>(data));
+        return left.addToTree(data);
+      }
+      if (right == null)
+        return (right = new SimpleNode<T>(data));
+      return right.addToTree(data);
+    }
+  }
+
+  public static <T extends Comparable<? super T>> boolean areLeavesSame(Node<T> node1, Node<T> node2)
+  {
+    Stack<Node<T>> stack1 = new Stack<Node<T>>();
+    Stack<Node<T>> stack2 = new Stack<Node<T>>();
+    stack1.push(node1);
+    stack2.push(node2);
+    // NOT using short-circuit operator
+    while (((node1 = advanceToLeaf(stack1)) != null) & ((node2 = advanceToLeaf(stack2)) != null))
+      if (!node1.getData().equals(node2.getData()))
+        return false;
+    // Return true if finished at same time
+    return (node1 == null) && (node2 == null);
+  }
+
+  private static <T extends Comparable<? super T>> Node<T> advanceToLeaf(Stack<Node<T>> stack)
+  {
+    while (!stack.isEmpty())
+    {
+      Node<T> node = stack.pop();
+      if (node.isLeaf())
+        return node;
+      Node<T> rightNode = node.getRight();
+      if (rightNode != null)
+        stack.push(rightNode);
+      Node<T> leftNode = node.getLeft();
+      if (leftNode != null)
+        stack.push(leftNode);
+    }
+    return null;
+  }
+
+  public static void main(String[] args)
+  {
+    SimpleNode<Integer> headNode1 = new SimpleNode<Integer>(35, new SimpleNode<Integer>(25, new SimpleNode<Integer>(15, new SimpleNode<Integer>(10), new SimpleNode<Integer>(20)), new SimpleNode<Integer>(30)), new SimpleNode<Integer>(45, new SimpleNode<Integer>(40), new SimpleNode<Integer>(50)));
+    SimpleNode<Integer> headNode2 = new SimpleNode<Integer>(24, new SimpleNode<Integer>(14, new SimpleNode<Integer>(10), new SimpleNode<Integer>(16, null, new SimpleNode<Integer>(20))), new SimpleNode<Integer>(34, new SimpleNode<Integer>(30), new SimpleNode<Integer>(42, new SimpleNode<Integer>(40), new SimpleNode<Integer>(56, new SimpleNode<Integer>(50), null))));
+    SimpleNode<Integer> headNode3 = new SimpleNode<Integer>(24, new SimpleNode<Integer>(14, new SimpleNode<Integer>(10), new SimpleNode<Integer>(16, null, new SimpleNode<Integer>(20))), new SimpleNode<Integer>(34, new SimpleNode<Integer>(30), new SimpleNode<Integer>(42, new SimpleNode<Integer>(40), new SimpleNode<Integer>(50, null, new SimpleNode<Integer>(56)))));
+    System.out.print("Leaves for set 1: ");
+    simpleWalk(headNode1);
+    System.out.println();
+    System.out.print("Leaves for set 2: ");
+    simpleWalk(headNode2);
+    System.out.println();
+    System.out.print("Leaves for set 3: ");
+    simpleWalk(headNode3);
+    System.out.println();
+    System.out.println("areLeavesSame(1, 2)? " + areLeavesSame(headNode1, headNode2));
+    System.out.println("areLeavesSame(2, 3)? " + areLeavesSame(headNode2, headNode3));
+  }
+
+  public static void simpleWalk(Node<Integer> node)
+  {
+    if (node.isLeaf())
+      System.out.print(node.getData() + " ");
+    else
+    {
+      Node<Integer> left = node.getLeft();
+      if (left != null)
+        simpleWalk(left);
+      Node<Integer> right = node.getRight();
+      if (right != null)
+        simpleWalk(right);
+    }
+  }
+}

Task/Same-Fringe/OCaml/same-fringe.ocaml

@@ -0,0 +1,23 @@
+type 'a btree = Leaf of 'a | BTree of ('a btree * 'a btree)
+
+let rec next = function
+  | [] -> None
+  | h :: t -> match h with
+    | Leaf x -> Some (x,t)
+    | BTree(a,b) -> next (a::b::t)
+
+let samefringe t1 t2 =
+  let rec aux s1 s2 = match (next s1, next s2) with
+    | None, None -> true
+    | None, _ | _, None -> false
+    | Some(a,b), Some(c,d) -> (a=c) && aux b d in
+  aux [t1] [t2]
+
+(* Test: *)
+let () =
+  let u = BTree(Leaf 1, BTree(Leaf 2, Leaf 3)) in
+  let v = BTree(BTree(Leaf 1, Leaf 2), Leaf 3) in
+  let w = BTree(BTree(Leaf 3, Leaf 2), Leaf 1) in
+  let check a b =
+    print_endline (if samefringe a b then "same" else "different") in
+  check u v; check v u; check v w;

Task/Same-Fringe/Perl-6/same-fringe-1.pl6

@@ -0,0 +1,8 @@
+sub fringe ($tree) {
+    multi sub fringey (Pair $node) { fringey $_ for $node.kv; }
+    multi sub fringey ( Any $leaf) { take $leaf; }
+
+    (gather fringey $tree), Cool;
+}
+
+sub samefringe ($a, $b) { all fringe($a) Z=== fringe($b) }

Task/Same-Fringe/Perl-6/same-fringe-2.pl6

@@ -0,0 +1,15 @@
+my $a = 1 => 2 => 3 => 4 => 5 => 6 => 7 => 8;
+my $b = 1 => (( 2 => 3 ) => (4 => (5 => ((6 => 7) => 8))));
+my $c = (((1 => 2) => 3) => 4) => 5 => 6 => 7 => 8;
+
+my $x = 1 => 2 => 3 => 4 => 5 => 6 => 7 => 8 => 9;
+my $y = 0 => 2 => 3 => 4 => 5 => 6 => 7 => 8;
+my $z = 1 => 2 => (4 => 3) => 5 => 6 => 7 => 8;
+
+say  so samefringe $a, $a;
+say  so samefringe $a, $b;
+say  so samefringe $a, $c;
+
+say not samefringe $a, $x;
+say not samefringe $a, $y;
+say not samefringe $a, $z;

Task/Same-Fringe/PicoLisp/same-fringe-1.l

@@ -0,0 +1,19 @@
+(de nextLeaf (Rt Tree)
+   (co Rt
+      (recur (Tree)
+         (when Tree
+            (recurse (cadr Tree))
+            (yield (car Tree))
+            (recurse (cddr Tree)) ) ) ) )
+
+(de cmpTrees (Tree1 Tree2)
+   (prog1
+      (use (Node1 Node2)
+         (loop
+            (setq
+               Node1 (nextLeaf "rt1" Tree1)
+               Node2 (nextLeaf "rt2" Tree2) )
+            (T (nor Node1 Node2) T)
+            (NIL (= Node1 Node2)) ) )
+      (co "rt1")
+      (co "rt2") ) )

Task/Same-Fringe/PicoLisp/same-fringe-2.l

@@ -0,0 +1,27 @@
+: (balance '*Tree1 (range 1 7))
+-> NIL
+: (for N (5 4 6 3 7 1 2) (idx '*Tree2 N T))
+-> NIL
+
+: (view *Tree1 T)
+      7
+   6
+      5
+4
+      3
+   2
+      1
+-> NIL
+
+: (view *Tree2 T)
+      7
+   6
+5
+   4
+      3
+            2
+         1
+-> NIL
+
+: (cmpTrees *Tree1 *Tree2)
+-> T

Task/Same-Fringe/Python/same-fringe.py

@@ -0,0 +1,35 @@
+try:
+    from itertools import zip_longest as izip_longest # Python 3.x
+except:
+    from itertools import izip_longest                # Python 2.6+
+
+def fringe(tree):
+    """Yield tree members L-to-R depth first,
+    as if stored in a binary tree"""
+    for node1 in tree:
+        if isinstance(node1, tuple):
+            for node2 in fringe(node1):
+                yield node2
+        else:
+            yield node1
+
+def same_fringe(tree1, tree2):
+    return all(node1 == node2 for node1, node2 in
+               izip_longest(fringe(tree1), fringe(tree2)))
+
+if __name__ == '__main__':
+    a = 1, 2, 3, 4, 5, 6, 7, 8
+    b = 1, (( 2, 3 ), (4, (5, ((6, 7), 8))))
+    c = (((1, 2), 3), 4), 5, 6, 7, 8
+
+    x = 1, 2, 3, 4, 5, 6, 7, 8, 9
+    y = 0, 2, 3, 4, 5, 6, 7, 8
+    z = 1, 2, (4, 3), 5, 6, 7, 8
+
+    assert same_fringe(a, a)
+    assert same_fringe(a, b)
+    assert same_fringe(a, c)
+
+    assert not same_fringe(a, x)
+    assert not same_fringe(a, y)
+    assert not same_fringe(a, z)

Task/Same-Fringe/REXX/same-fringe-1.rexx

@@ -0,0 +1,176 @@
+/* REXX ***************************************************************
+* Same Fringe
+*           1                A                 A
+*          / \              / \               / \
+*         /   \            /   \             /   \
+*        /     \          /     \           /     \
+*       2       3        B       C         B       C
+*      / \     /        / \     /         / \     /
+*     4   5   6        D   E   F         D   E   F
+*    /       / \      /       / \       /       / \
+*   7       8   9    G       H   I     G       *   I
+*
+* 23.08.2012 Walter Pachl derived from
+*                            http://rosettacode.org/wiki/Tree_traversal
+* Tree A: A B D G E C F H I
+* Tree B: A B D G E C F * I
+**********************************************************************/
+debug=0
+node.=0
+lvl=0
+
+Call mktree 'A'
+Call mktree 'B'
+
+done.=0
+za=root.a; leafa=node.a.za.0name
+zb=root.a; leafb=node.b.zb.0name
+done.a.za=1
+done.b.zb=1
+Do i=1 To 12
+  if leafa=leafb Then Do
+    If leafa=0 Then Do
+      Say 'Fringes are equal'
+      Leave
+      End
+    Say leafa '=' leafb
+    Do j=1 To 12 Until done.a.za=0
+      za=go_next(za,'A'); leafa=node.a.za.0name
+      End
+    done.a.za=1
+    Do j=1 To 12 Until done.b.zb=0
+      zb=go_next(zb,'B'); leafb=node.b.zb.0name
+      End
+    done.b.zb=1
+    End
+  Else Do
+    Select
+      When leafa=0 Then
+        Say leafb 'exceeds leaves in tree A'
+      When leafb=0 Then
+        Say leafa 'exceeds leaves in tree B'
+      Otherwise
+        Say 'First difference' leafa '<>' leafb
+      End
+    Leave
+    End
+  End
+Exit
+
+
+note:
+/**********************************************************************
+* add the node to the preorder list unless it's already there
+* add the node to the level list
+**********************************************************************/
+  Parse Arg z,t
+  If z<>0 &,                           /* it's a node                */
+     done.z=0 Then Do                  /* not yet done               */
+    wl.t=wl.t z                        /* add it to the preorder list*/
+    ll.lvl=ll.lvl z                    /* add it to the level list   */
+    done.z=1                           /* remember it's done         */
+    leafl=leafl node.t.z.0name
+    End
+  Return
+
+go_next: Procedure Expose node. lvl
+/**********************************************************************
+* find the next node to visit in the treewalk
+**********************************************************************/
+  next=0
+  Parse arg z,t
+  If node.t.z.0left<>0 Then Do         /* there is a left son        */
+    If node.t.z.0left.done=0 Then Do   /* we have not visited it     */
+      next=node.t.z.0left              /* so we go there             */
+      node.t.z.0left.done=1            /* note we were here          */
+      lvl=lvl+1                        /* increase the level         */
+      End
+    End
+  If next=0 Then Do                    /* not moved yet              */
+    If node.t.z.0rite<>0 Then Do       /* there is a right son       */
+      If node.t.z.0rite.done=0 Then Do /* we have not visited it     */
+        next=node.t.z.0rite            /* so we go there             */
+        node.t.z.0rite.done=1          /* note we were here          */
+        lvl=lvl+1                      /* increase the level         */
+        End
+      End
+    End
+  If next=0 Then Do                    /* not moved yet              */
+    next=node.t.z.0father              /* go to the father           */
+    lvl=lvl-1                          /* decrease the level         */
+    End
+  Return next                          /* that's the next node       */
+                                       /* or zero if we are done     */
+
+mknode: Procedure Expose node.
+/**********************************************************************
+* create a new node
+**********************************************************************/
+  Parse Arg name,t
+  z=node.t.0+1
+  node.t.z.0name=name
+  node.t.z.0father=0
+  node.t.z.0left =0
+  node.t.z.0rite =0
+  node.t.0=z
+  Return z                        /* number of the node just created */
+
+attleft: Procedure Expose node.
+/**********************************************************************
+* make son the left son of father
+**********************************************************************/
+  Parse Arg son,father,t
+  node.t.son.0father=father
+  z=node.t.father.0left
+  If z<>0 Then Do
+    node.t.z.0father=son
+    node.t.son.0left=z
+    End
+  node.t.father.0left=son
+  Return
+
+attrite: Procedure Expose node.
+/**********************************************************************
+* make son the right son of father
+**********************************************************************/
+  Parse Arg son,father,t
+  node.t.son.0father=father
+  z=node.t.father.0rite
+  If z<>0 Then Do
+    node.t.z.0father=son
+    node.t.son.0rite=z
+    End
+  node.t.father.0rite=son
+  le=node.t.father.0left
+  If le>0 Then
+    node.t.le.0brother=node.t.father.0rite
+  Return
+
+mktree: Procedure Expose node. root.
+/**********************************************************************
+* build the tree according to the task
+**********************************************************************/
+  Parse Arg t
+  If t='A' Then Do
+    a=mknode('A',t); root.t=a
+    b=mknode('B',t); Call attleft b,a,t
+    c=mknode('C',t); Call attrite c,a,t
+    d=mknode('D',t); Call attleft d,b,t
+    e=mknode('E',t); Call attrite e,b,t
+    f=mknode('F',t); Call attleft f,c,t
+    g=mknode('G',t); Call attleft g,d,t
+    h=mknode('H',t); Call attleft h,f,t
+    i=mknode('I',t); Call attrite i,f,t
+    End
+  Else Do
+    a=mknode('A',t); root.t=a
+    b=mknode('B',t); Call attleft b,a,t
+    c=mknode('C',t); Call attrite c,a,t
+    d=mknode('D',t); Call attleft d,b,t
+    e=mknode('E',t); Call attrite e,b,t
+    f=mknode('F',t); Call attleft f,c,t
+    g=mknode('G',t); Call attleft g,d,t
+    h=mknode('*',t); Call attleft h,f,t
+    i=mknode('I',t); Call attrite i,f,t
+    End
+  Return

Task/Same-Fringe/REXX/same-fringe-2.rexx

@@ -0,0 +1,139 @@
+/* REXX ***************************************************************
+* Same Fringe
+=           1                A                 A
+=          / \              / \               / \
+=         /   \            /   \             /   \
+=        /     \          /     \           /     \
+=       2       3        B       C         B       C
+=      / \     /        / \     /         / \     /
+=     4   5   6        D   E   F         D   E   F
+=    /       / \      /       / \       /       / \
+=   7       8   9    G       H   I     G       *   I
+=
+* 23.08.2012 Walter Pachl derived from
+*                            http://rosettacode.org/wiki/Tree_traversal
+* Tree A: A B D G E C F H I
+* Tree B: A B D G E C F * I
+**********************************************************************/
+node.=0
+
+Call mktree 'A'
+Call mktree 'B'
+
+sideboard.=0
+
+za=root.a; leafa=node.a.za.0name
+zb=root.b; leafb=node.b.zb.0name
+Do i=1 To 20 Until za=0 & zb=0
+  If leafa=leafb Then Do
+    Say leafa '=' leafb
+    Parse Value get_next(za,'A') with za leafa
+    Parse Value get_next(zb,'B') with zb leafb
+    End
+  Else Do
+    Select
+      When za=0 Then Say leafb 'exceeds tree A'
+      When zb=0 Then Say leafa 'exceeds tree B'
+      Otherwise Say 'First difference' leafa '<>' leafb
+      End
+    Leave
+    Exit
+    End
+  End
+exit
+
+get_next: Procedure Expose node. sideboard.
+  Parse Arg za,t
+  Select
+    When node.t.za.0left<>0 Then Do
+      If node.t.za.0rite<>0 Then Do
+        z=sideboard.t.0+1
+        sideboard.t.z=node.t.za.0rite
+        sideboard.t.0=z
+        End
+      za=node.t.za.0left
+      End
+    When node.t.za.0rite<>0 Then Do
+      za=node.t.za.0rite
+      End
+    Otherwise Do
+      z=sideboard.t.0
+      za=sideboard.t.z
+      z=z-1
+      sideboard.t.0=z
+      End
+    End
+  Return za node.t.za.0name
+
+mknode: Procedure Expose node.
+/**********************************************************************
+* create a new node
+**********************************************************************/
+  Parse Arg name,t
+  z=node.t.0+1
+  node.t.z.0name=name
+  node.t.z.0father=0
+  node.t.z.0left =0
+  node.t.z.0rite =0
+  node.t.0=z
+  Return z                        /* number of the node just created */
+
+attleft: Procedure Expose node.
+/**********************************************************************
+* make son the left son of father
+**********************************************************************/
+  Parse Arg son,father,t
+  node.t.son.0father=father
+  z=node.t.father.0left
+  If z<>0 Then Do
+    node.t.z.0father=son
+    node.t.son.0left=z
+    End
+  node.t.father.0left=son
+  Return
+
+attrite: Procedure Expose node.
+/**********************************************************************
+* make son the right son of father
+**********************************************************************/
+  Parse Arg son,father,t
+  node.t.son.0father=father
+  z=node.t.father.0rite
+  If z<>0 Then Do
+    node.t.z.0father=son
+    node.t.son.0rite=z
+    End
+  node.t.father.0rite=son
+  le=node.t.father.0left
+  If le>0 Then
+    node.t.le.0brother=node.t.father.0rite
+  Return
+
+mktree: Procedure Expose node. root.
+/**********************************************************************
+* build the tree according to the task
+**********************************************************************/
+  Parse Arg t
+  If t='A' Then Do
+    a=mknode('A',t); root.t=a
+    b=mknode('B',t); Call attleft b,a,t
+    c=mknode('C',t); Call attrite c,a,t
+    d=mknode('D',t); Call attleft d,b,t
+    e=mknode('E',t); Call attrite e,b,t
+    f=mknode('F',t); Call attleft f,c,t
+    g=mknode('G',t); Call attleft g,d,t
+    h=mknode('H',t); Call attleft h,f,t
+    i=mknode('I',t); Call attrite i,f,t
+    End
+  Else Do
+    a=mknode('A',t); root.t=a
+    b=mknode('B',t); Call attleft b,a,t
+    c=mknode('C',t); Call attrite c,a,t
+    d=mknode('D',t); Call attleft d,b,t
+    e=mknode('E',t); Call attrite e,b,t
+    f=mknode('F',t); Call attleft f,c,t
+    g=mknode('G',t); Call attleft g,d,t
+    h=mknode('*',t); Call attleft h,f,t
+    i=mknode('I',t); Call attrite i,f,t
+    End
+  Return

Task/Same-Fringe/REXX/same-fringe-3.rexx

@@ -0,0 +1,87 @@
+/*REXX pgm examines leaves of two binary trees.   Tree used is as above.*/
+_=left('',28);  say _ '        A                                   A     '
+                say _ '       / \    ◄────1st tree                / \    '
+                say _ '      /   \                               /   \   '
+                say _ '     /     \                             /     \  '
+                say _ '    B       C                           B       C '
+                say _ '   / \     /          2nd tree────►    / \     /  '
+                say _ '  D   E   F                           D   E   F   '
+                say _ ' /       / \                         /       / \  '
+                say _ 'G       H   I                       G       δ   I '
+say;  #=0                              /*#: # of leaves.                */
+parse var #  done.  1  node.           /*set all these variables to zero*/
+call make_tree  '1st'
+call make_tree  '2nd'
+z1=root.1st;  L1=node.1st.z1;  done.1st.z1=1  /*L1 is a leaf on 1st tree*/
+z2=z1;        L2=node.2nd.z2;  done.2nd.z2=1  /*L2  " "   "   " 2nd   " */
+
+  do #%2                               /*loop for the number of leaves. */
+  if L1==L2 then do
+                 if L1==0  then call sayX  'The trees are equal.'
+                 say  '    The '  L1  " leaf is identical in both trees."
+                    do  until  \done.1st.z1
+                    z1=go_next(z1,'1st');   L1=node.1st.z1
+                    end
+                 done.1st.z1=1
+                    do  until  \done.2nd.z2
+                    z2=go_next(z2,'2nd');   L2=node.2nd.z2
+                    end
+                 done.2nd.z2=1
+                 end
+            else select
+                 when L1==0 then call sayX L2 'exceeds leaves in 1st tree'
+                 when L2==0 then call sayX L1 'exceeds leaves in 2nd tree'
+                 otherwise       call sayX 'A difference is: ' L1 '¬=' L2
+                 end   /*select*/
+  end   /*#%2*/
+exit
+/*──────────────────────────────────GO_NEXT subroutine──────────────────*/
+go_next: procedure expose node.;   arg q,t             /*find next node.*/
+next=0
+if node.t.q._Lson\==0 then             /*is there a left branch in tree?*/
+  if node.t.q._Lson.done==0 then do    /*has this node been visited yet?*/
+                                 next=node.t.q._Lson   /*──► next node. */
+                                 node.t.q._Lson.done=1 /*mark Lson done.*/
+                                 end
+if next==0 then
+  if node.t.q._Rson\==0 then           /*is there a right tree branch ? */
+    if node.t.q._Rson.done==0 then do  /*has this node been visited yet?*/
+                                   next=node.t.q._Rson   /*──► next node*/
+                                   node.t.q._Rson.done=1 /*mark Rson don*/
+                                   end
+if next==0 then next=node.t.q._dad     /*process the  father  node.     */
+return next                            /*the next node  (or 0, if done).*/
+/*──────────────────────────────────MAKE_NODE subroutine────────────────*/
+make_node: parse arg name,t;   # = #+1 /*make a new node/branch on tree.*/
+q = node.t.0 + 1;         node.t.q = name;          node.t.q._dad = 0
+node.t.q._Lson = 0;       node.t.q._Rson = 0;       node.t.0 = q
+return q                               /*number of the node just created*/
+/*──────────────────────────────────MAKE_TREE subroutine────────────────*/
+make_tree: procedure expose node. root. #;  arg tree     /*build a tree.*/
+                     hhh='δ'           /*the odd duck in the whole tree.*/
+if tree=='1ST'  then hhh='H'
+                             a=make_node('A',tree);            root.tree=a
+                             b=make_node('B',tree);   call sonL b,a,tree
+                             c=make_node('C',tree);   call sonR c,a,tree
+                             d=make_node('D',tree);   call sonL d,b,tree
+                             e=make_node('E',tree);   call sonR e,b,tree
+                             f=make_node('F',tree);   call sonL f,c,tree
+                             g=make_node('G',tree);   call sonL g,d,tree
+                /*quack?*/   h=make_node(hhh,tree);   call sonL h,f,tree
+                             i=make_node('I',tree);   call sonR i,f,tree
+return
+/*──────────────────────────────────SAYX subroutine─────────────────────*/
+sayX: say;      say arg(1);  say;        exit         /*tell msg & exit.*/
+/*──────────────────────────────────SONL subroutine─────────────────────*/
+sonL: procedure expose node.; parse arg son,dad,t     /*build left son. */
+                    node.t.son._dad=dad;      q=node.t.dad._Lson
+if q\==0  then do;  node.t.q._dad=son;        node.t.son._Lson=q;   end
+node.t.dad._Lson=son
+return
+/*──────────────────────────────────SONR subroutine─────────────────────*/
+sonR: procedure expose node.; parse arg son,dad,t     /*build right son.*/
+                    node.t.son._dad=dad;       q=node.t.dad._Rson
+if q\==0  then do;  node.t.q._dad=son;         node.t.son._Rson=q;     end
+node.t.dad._Rson=son
+if node.t.dad._Lson>0  then node.t.le._brother=node.t.dad._Rson
+return

Task/Same-Fringe/Racket/same-fringe.rkt

@@ -0,0 +1,30 @@
+#lang racket
+(require racket/control)
+
+(define (make-fringe-getter tree)
+  (λ ()
+    (let loop ([tree tree])
+      (match tree
+        [(cons a d) (loop a)
+                    (loop d)]
+        ['()        (void)]
+        [else       (fcontrol tree)]))
+    (fcontrol 'done)))
+
+(define (same-fringe? tree1 tree2)
+  (let loop ([get-fringe1 (make-fringe-getter tree1)]
+             [get-fringe2 (make-fringe-getter tree2)])
+    (% (get-fringe1)
+       (λ (fringe1 get-fringe1)
+         (% (get-fringe2)
+            (λ (fringe2 get-fringe2)
+              (and (equal? fringe1 fringe2)
+                   (or (eq? fringe1 'done)
+                       (loop get-fringe1 get-fringe2)))))))))
+
+;; unit tests
+(require rackunit)
+(check-true (same-fringe? '((1 2 3) ((4 5 6) (7 8)))
+                          '(((1 2 3) (4 5 6)) (7 8))))
+(check-false (same-fringe? '((1 2 3) ((4 5 6) (7 8)))
+                           '(((1 2 3) (4 6)) (8))))

Task/Same-Fringe/Tcl/same-fringe-1.tcl

@@ -0,0 +1,33 @@
+package require Tcl 8.6
+package require struct::tree
+
+# A wrapper round a coroutine for iterating over the leaves of a tree in order
+proc leafiterator {tree} {
+    coroutine coro[incr ::coroutines] apply {tree {
+	yield [info coroutine]
+	$tree walk [$tree rootname] node {
+	    if {[$tree isleaf $node]} {
+		yield $node
+	    }
+	}
+	yieldto break
+    }} $tree
+}
+
+# Compare two trees for equality of their leaf node names
+proc samefringe {tree1 tree2} {
+    set c1 [leafiterator $tree1]
+    set c2 [leafiterator $tree2]
+    try {
+	while 1 {
+	    if {[set l1 [$c1]] ne [set l2 [$c2]]} {
+		puts "$l1 != $l2";    # Just so we can see where we failed
+		return 0
+	    }
+	}
+	return 1
+    } finally {
+	rename $c1 {}
+	rename $c2 {}
+    }
+}

Task/Same-Fringe/Tcl/same-fringe-2.tcl

@@ -0,0 +1,20 @@
+# Make some trees to compare...
+struct::tree t1 deserialize {
+    root {} {}
+      a 0 {}
+        d 3 {}
+        e 3 {}
+      b 0 {}
+      c 0 {}
+}
+struct::tree t2 deserialize {
+    root {} {}
+      a 0 {}
+        d 3 {}
+        e 3 {}
+      b 0 {}
+      cc 0 {}
+}
+
+# Print the boolean result of doing the comparison
+puts [samefringe t1 t2]