2019: d04: ex2: add solution

2019/d04/ex2/ex2.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python
+
+from typing import Iterator
+
+
+def is_valid_password(p: int) -> bool:
+    digits = str(p)
+
+    def has_unique_adjacent_digit():
+        counts = {d: 0 for d in range(10)}
+        for (a, b) in zip(digits, digits[1:]):
+            if a == b:
+                counts[int(a)] += 1
+        return any(count == 1 for count in counts.values())
+
+    def digits_never_decrease():
+        return all(a == b for a, b in zip(sorted(digits), digits))
+
+    return has_unique_adjacent_digit() and digits_never_decrease()
+
+
+def compute_pass(begin: int, end: int) -> Iterator[int]:
+    for p in range(begin, end + 1):
+        if is_valid_password(p):
+            yield p
+
+
+def main() -> None:
+    begin = 264793
+    end = 803935
+    print(sum(1 for p in compute_pass(begin, end)))
+
+
+if __name__ == "__main__":
+    main()