Create 32_Longest_Valid_Parentheses.md

Author: koji

32_Longest_Valid_Parentheses.md

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+## 32. Longest Valid Parentheses
+
+
+Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.
+
+
+Example 1:
+
+Input: s = "(()"
+Output: 2
+Explanation: The longest valid parentheses substring is "()".
+Example 2:
+
+Input: s = ")()())"
+Output: 4
+Explanation: The longest valid parentheses substring is "()()".
+Example 3:
+
+Input: s = ""
+Output: 0
+ 
+
+Constraints:
+
+0 <= s.length <= 3 * 104
+s[i] is '(', or ')'.
+
+
+```python
+def longestValidParentheses(self, s: str) -> int:
+ if len(s) ==0: return 0
+ stack = [-1]
+ maxLen = 0
+ for i in range(len(s)):
+ if s[i] == '(':
+ stack.append(i)
+ else:
+ stack.pop()
+ if len(stack) == 0:
+ stack.append(i)
+ else:
+ maxLen = max(i-stack[-1], maxLen)
+ return maxLen
+```
+
+```
+Runtime: 32 ms, faster than 99.13% of Python3 online submissions for Longest Valid Parentheses.
+Memory Usage: 14.4 MB, less than 5.50% of Python3 online submissions for Longest Valid Parentheses.
+```