[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Author: pre-commit-ci[bot]

strings/longest_valid_paranthesis.py

@@ -28,6 +28,9 @@ def longest_valid_parenthesis(self, s: str) -> int:
     while stack:
         res = max(res, stack.pop())
     return res * 2
+
+
 if __name__ == "__main__":
     from doctest import testmod
+
     testmod()