Given a string containing just the characters '(' and ')', return 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 "()()".
class Solution {
public int longestValidParentheses(String s) {
Stack<Integer> stack = new Stack();
stack.push(-1);
int maxLen = 0;
for(int i = 0; i < s.length(); i++)
{
if(s.charAt(i) == '(')
stack.push(i);
else if(s.charAt(i) == ')')
{
stack.pop();
if(stack.empty())
stack.push(i);
else
maxLen = Math.max(maxLen, i - stack.peek());
}
}
return maxLen;
}
}
