September 2017 Update

Task/Cut-a-rectangle/Rust/cut-a-rectangle.rust

@@ -0,0 +1,73 @@
+fn cwalk(mut vis: &mut Vec<Vec<bool>>, count: &mut isize, w: usize, h: usize, y: usize, x: usize, d: usize) {
+    if x == 0 || y == 0 || x == w || y == h {
+        *count += 1;
+        return;
+    }
+
+    vis[y][x] = true;
+    vis[h - y][w - x] = true;
+
+    if x != 0 && ! vis[y][x - 1] {
+        cwalk(&mut vis, count, w, h, y, x - 1, d | 1);
+    }
+    if d & 1 != 0 && x < w && ! vis[y][x+1] {
+        cwalk(&mut vis, count, w, h, y, x + 1, d | 1);
+    }
+    if y != 0 && ! vis[y - 1][x] {
+        cwalk(&mut vis, count, w, h, y - 1, x, d | 2);
+    }
+    if d & 2 != 0 && y < h && ! vis[y + 1][x] {
+        cwalk(&mut vis, count, w, h, y + 1, x, d | 2);
+    }
+
+    vis[y][x] = false;
+    vis[h - y][w - x] = false;
+}
+
+fn count_only(x: usize, y: usize) -> isize {
+    let mut count = 0;
+    let mut w = x;
+    let mut h = y;
+
+    if (h * w) & 1 != 0 {
+        return count;
+    }
+    if h & 1 != 0 {
+        std::mem::swap(&mut w, &mut h);
+    }
+
+    let mut vis = vec![vec![false; w + 1]; h + 1];
+    vis[h / 2][w / 2] = true;
+
+    if w & 1 != 0 {
+        vis[h / 2][w / 2 + 1] = true;
+    }
+    let mut res;
+    if w > 1 {
+        cwalk(&mut vis, &mut count, w, h, h / 2, w / 2 - 1, 1);
+        res = 2 * count - 1;
+        count = 0;
+        if w != h {
+            cwalk(&mut vis, &mut count, w, h, h / 2 + 1, w / 2, if w & 1 != 0 { 3 } else { 2 });
+        }
+        res += 2 * count - if w & 1 == 0 { 1 } else { 0 };
+    }
+    else {
+        res = 1;
+    }
+
+    if w == h {
+        res = 2 * res + 2;
+    }
+    res
+}
+
+fn main() {
+    for y in 1..10 {
+        for x in 1..y + 1 {
+            if x & 1 == 0 || y & 1 == 0 {
+                println!("{} x {}: {}", y, x, count_only(x, y));
+            }
+        }
+    }
+}