Solve more problems road to 200.

python/e164.py

@@ -0,0 +1,25 @@
+from functools import lru_cache
+
+
+@lru_cache
+def count(last, left):
+    if left == 0:
+        return 1
+    c = 0
+    for d in range(10):
+        if sum(last) + d <= 9:
+            c += count((last[-1], d), left - 1)
+    return c
+
+
+def euler_164():
+    c = 0
+    for d in range(1, 10):
+        c += count((d, ), 20-1)
+    return c
+
+
+if __name__ == "__main__":
+    solution = euler_164()
+    print("e164.py: " + str(solution))
+    assert solution == 378158756814587