Initial data commit

Task/Deepcopy/Go/deepcopy-2.go

@@ -0,0 +1,60 @@
+package main
+
+import "fmt"
+
+// a type that allows cyclic structures
+type node []*node
+
+// recursively print the contents of a node
+func (n *node) list() {
+    if n == nil {
+        fmt.Println(n)
+        return
+    }
+    listed := map[*node]bool{nil: true}
+    var r func(*node)
+    r = func(n *node) {
+        listed[n] = true
+        fmt.Printf("%p -> %v\n", n, *n)
+        for _, m := range *n {
+            if !listed[m] {
+                r(m)
+            }
+        }
+    }
+    r(n)
+}
+
+// construct a deep copy of a node
+func (n *node) ccopy() *node {
+    if n == nil {
+        return n
+    }
+    cc := map[*node]*node{nil: nil}
+    var r func(*node) *node
+    r = func(n *node) *node {
+        c := make(node, len(*n))
+        cc[n] = &c
+        for i, m := range *n {
+            d, ok := cc[m]
+            if !ok {
+                d = r(m)
+            }
+            c[i] = d
+        }
+        return &c
+    }
+    return r(n)
+}
+
+func main() {
+    a := node{nil}
+    c := &node{&node{&a}}
+    a[0] = c
+    c.list()
+    cc := c.ccopy()
+    fmt.Println("copy:")
+    cc.list()
+    fmt.Println("original:")
+    c.list()
+}