Solve Euler 174

python/e174.py

@@ -0,0 +1,42 @@
+from collections import defaultdict
+
+
+def tiles(size):
+    """ Returns the number of tiles for a square of the given size. """
+    return size * 4 - 4
+
+
+def tiles_for_outer(size, ts, limit):
+    """ Adds t to ts for given outer size as long as t is
+    smaller than the limit. """
+    t = tiles(size)
+    if t > limit:
+        return
+    ts[t] += 1
+    for ni in range(size - 2, 2, -2):
+        t += tiles(ni)
+        if t > limit:
+            break
+        ts[t] += 1
+
+
+def euler_173():
+    ts = defaultdict(int)
+    limit = 1_000_000
+
+    for outer_size in range(3, limit // 4):
+        tiles_for_outer(outer_size, ts, limit)
+
+    c = 0
+    for n in range(1, 11):
+        for v in ts.values():
+            if v == n:
+                c += 1
+
+    return c
+
+
+if __name__ == "__main__":
+    solution = euler_173()
+    print("e173.py: " + str(solution))
+    assert solution == 209566