Solve day 11

11_fuelcells.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+serial = 5791
+w = 300
+grid = w * w * [0]
+
+for y in range(w):
+    for x in range(w):
+        rack = x + 11
+        grid[y * w + x] = (rack * (y + 1) + serial) * rack // 100 % 10 - 5
+
+for i in range(len(grid)):
+    y, x = divmod(i, w)
+    top = grid[i - w] if y else 0
+    left = grid[i - 1] if x else 0
+    topleft = grid[i - w - 1] if x and y else 0
+    grid[i] += top + left - topleft
+
+def squares(sz):
+    for y in range(w - sz + 1):
+        for x in range(w - sz + 1):
+            s = grid[(y + sz - 1) * w + (x + sz - 1)]
+            if y and x: s += grid[(y - 1) * w + (x - 1)]
+            if x: s -= grid[(y + sz - 1) * w + (x - 1)]
+            if y: s -= grid[(y - 1) * w + (x + sz - 1)]
+            yield s, x + 1, y + 1
+
+s, x, y = max(squares(3))
+print(x, y, sep=',')
+
+s, x, y, sz = max(max(squares(sz)) + (sz,) for sz in range(1, w + 1))
+print(x, y, sz, sep=',')