Just another update

Task/Maze-solving/00DESCRIPTION

@@ -1,5 +1,4 @@
-For a maze generated by [[Maze generation|this task]], write a function that
-finds (and displays) the shortest path between two cells. Note that because these
-mazes are generated by the [[wp:Maze_generation_algorithm#Depth-first_search|Depth-first search]]
-algorithm, they contain no circular paths, and a simple depth-first tree search
-can be used.
+For a maze generated by [[Maze generation|this task]], write a function
+that finds (and displays) the shortest path between two cells.
+Note that because these mazes are generated by the [[wp:Maze_generation_algorithm#Depth-first_search|Depth-first search]] algorithm, they contain no circular paths,
+and a simple depth-first tree search can be used.

Task/Maze-solving/00META.yaml

@@ -1,4 +1,5 @@
 ---
 category:
 - Recursion
+- Puzzles
 note: Games

Task/Maze-solving/D/maze-solving.d

@@ -1,16 +1,16 @@
 import std.stdio, std.random, std.string, std.array, std.algorithm,
-       std.file;
+       std.file, std.conv;
 
 enum int cx = 4, cy = 2; // Cell size x and y.
 enum int cx2 = cx / 2, cy2 = cy / 2;
 enum pathSymbol = '.';
 struct V2 { int x, y; }
 
-bool solveMaze(char[][] maze, in V2 s, in V2 end) pure nothrow {
+bool solveMaze(char[][] maze, in V2 s, in V2 end) pure nothrow @safe @nogc {
     if (s == end)
         return true;
 
-    foreach (d; [V2(0, -cy), V2(+cx, 0), V2(0, +cy), V2(-cx, 0)])
+    foreach (immutable d; [V2(0, -cy), V2(+cx, 0), V2(0, +cy), V2(-cx, 0)])
         if (maze[s.y + (d.y / 2)][s.x + (d.x / 2)] == ' ' &&
             maze[s.y + d.y][s.x + d.x] == ' ') {
             maze[s.y + d.y][s.x + d.x] = pathSymbol;
@@ -23,15 +23,13 @@ bool solveMaze(char[][] maze, in V2 s, in V2 end) pure nothrow {
 }
 
 void main() {
-    auto maze = "maze.txt".readText.splitLines.map!(r => r.dup).array;
-    immutable int h = ((cast(int)maze.length) - 1) / cy;
+    auto maze = "maze.txt".File.byLine.map!(r => r.chomp.dup).array;
+    immutable h = (maze.length.signed - 1) / cy;
     assert (h > 0);
-    immutable int w = ((cast(int)maze[0].length) - 1) / cx;
+    immutable w = (maze[0].length.signed - 1) / cx;
 
-    immutable start = V2(cx2 + cx * uniform(0, w),
-                         cy2 + cy * uniform(0, h));
-    immutable end = V2(cx2 + cx * uniform(0, w),
-                       cy2 + cy * uniform(0, h));
+    immutable start = V2(cx2 + cx * uniform(0, w), cy2 + cy * uniform(0, h));
+    immutable end = V2(cx2 + cx * uniform(0, w), cy2 + cy * uniform(0, h));
 
     maze[start.y][start.x] = pathSymbol;
     if (!solveMaze(maze, start, end))

Task/Maze-solving/J/maze-solving.j

@@ -1,3 +1,28 @@
+maze=:4 :0
+  assert.0<:n=.<:x*y
+  horiz=. 0$~x,y-1
+  verti=. 0$~(x-1),y
+  path=.,:here=. ?x,y
+  unvisited=.0 (<here+1)} 0,0,~|:0,0,~1$~y,x
+  while.n do.
+    neighbors=. here+"1 (,-)=0 1
+    neighbors=. neighbors #~ (<"1 neighbors+1) {unvisited
+    if.#neighbors do.
+      n=.n-1
+      next=. ({~ ?@#) neighbors
+      unvisited=.0 (<next+1)} unvisited
+      if.{.next=here
+      do. horiz=.1 (<-:here+next-0 1)} horiz
+      else. verti=. 1 (<-:here+next-1 0)} verti end.
+      path=.path,here=.next
+    else.
+      here=.{:path
+      path=.}:path
+    end.
+  end.
+  horiz;verti
+)
+
 NB. source Dijkstra_equal_weights graph
 NB.
 NB.        +   +---+---+
@@ -35,7 +60,7 @@ Dijkstra_equal_weights =: 4 : 0
  dist;previous
 )
 
-path =. 3 : 0
+path =: 3 : 0
   p =. <:#y
   while. _ > {:p do.
     p =. p,y{~{:p
@@ -56,7 +81,7 @@ solve=:3 :0
   path , > {: 0 Dijkstra_equal_weights graph
 )
 
-display=:3 :0 NB. Monadic display copied from maze generation task
+display=:3 :0
   size=. >.&$&>/y
   text=. (}:1 3$~2*1+{:size)#"1":size$<' '
   'hdoor vdoor'=. 2 4&*&.>&.> (#&,{@;&i./@$)&.> y
@@ -66,16 +91,5 @@ display=:3 :0 NB. Monadic display copied from maze generation task
   size=. >.&$&>/y
   columns=. {: size
   cells =. <"1(1 2&p.@<.@(%&columns) ,.  2 4&p.@(columns&|))x
-  '+' cells } a  NB. exercise, replace cells with a gerund to draw arrows on the path.
+  'o' cells } a  NB. exercise, replace cells with a gerund to draw arrows on the path.
 )
-
-   4 (display~ solve)@maze 9
-┌   ┬───┬───┬───┬───┬───┬───┬───┬───┐
-│ +         │           │           │
-├   ┼───┼   ┼   ┼   ┼───┼   ┼   ┼   ┤
-│ +   + │       │           │   │   │
-├───┼   ┼───┼───┼───┼───┼───┼   ┼───┤
-│   │ +   +   + │ +   +   + │       │
-├   ┼───┼───┼   ┼   ┼───┼   ┼───┼───┤
-│             +   + │     +   +   +
-└───┴───┴───┴───┴───┴───┴───┴───┴───┘