From 5373afb485b6d4a22d06a83a715eeaf6872e9eac Mon Sep 17 00:00:00 2001
From: mark <markichnich@proton.me>
Date: Sun, 27 Nov 2022 10:14:11 +0100
Subject: [PATCH] add d version.

---
 snail.d | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 snail.d

diff --git a/snail.d b/snail.d
new file mode 100644
index 0000000..6007971
--- /dev/null
+++ b/snail.d
@@ -0,0 +1,61 @@
+import std.stdio;
+import std.algorithm;
+
+T[] snail(T)(T[][] xss) 
+{
+    ulong h = xss.length;
+    if (h == 0) { return []; }
+    ulong w = xss[0].length;
+    if (w == 0) { return []; }
+
+    T[] v = [];
+
+    foreach (b; 0..((max(w, h) / 2)+1)) {
+        ulong ex = w - b - 1;
+        ulong ey = h - b - 1;
+
+        foreach (c; b..ex+1)
+            v ~= [xss[b][c]];
+        foreach (r; b+1..ey+1)
+            v ~= [xss[r][ex]];
+
+        if (ex == b || ey == b) {
+            return v;
+        }
+
+        foreach (o; b..ex)
+            v ~= [xss[ey][ex-1-o]];
+        foreach (o; b+1..ey)
+            v ~= [xss[ey-o][b]];
+    }
+    return v;
+}
+
+void main()
+{
+    int[][] initial = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
+    int[] expected = [1,2,3,6,9,8,7,4,5];
+
+    assert(snail(initial) == expected);
+    writeln(snail(initial) == expected);
+
+    initial = [[1, 2, 3, 4],  [5, 6, 7, 8],  [9, 10, 11, 12]];
+    expected = [1, 2, 3, 4, 8, 12, 11, 10, 9, 5, 6, 7];
+
+    assert(snail(initial) == expected);
+    writeln(snail(initial) == expected);
+
+    initial = [
+        [1, 2, 3], 
+        [4, 5, 6], 
+        [7, 8, 9], 
+        [10, 11, 12], 
+        [13, 14, 15]
+    ];
+    expected = [1, 2, 3, 6, 9, 12, 15, 14, 13, 10, 7, 4, 5, 8, 11];
+
+    assert(snail(initial) == expected);
+    writeln(snail(initial) == expected);
+
+    "all tests passed".writeln;
+}