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Task/Zig-zag-matrix/Nim/zig-zag-matrix.nim

@@ -0,0 +1,36 @@
+import algorithm, strutils
+
+type Pos = tuple[x, y: int]
+
+template newSeqWith(len: int, init: expr): expr =
+  var result {.gensym.} = newSeq[type(init)](len)
+  for i in 0 .. <len:
+    result[i] = init
+  result
+
+proc `$`(m: seq[seq[int]]): string =
+  result = ""
+  for r in m:
+    for c in r:
+      result.add align($c, 2) & " "
+    result.add "\n"
+
+proc zigzagMatrix(n): auto =
+  result = newSeqWith(n, newSeq[int](n))
+
+  var indices = newSeq[Pos]()
+
+  for x in 0 .. <n:
+    for y in 0 .. <n:
+      indices.add((x,y))
+
+  sort(indices, proc(a, b: Pos): int =
+    result = a.x + a.y - b.x - b.y
+    if result == 0: result =
+      (if (a.x + a.y) mod 2 == 0: a.y else: -a.y) -
+      (if (b.x + b.y) mod 2 == 0: b.y else: -b.y))
+
+  for i, p in indices:
+    result[p.x][p.y] = i
+
+echo zigzagMatrix(6)