Leetcode 32 Longest Valid Parentheses Solution in c++ | Hindi Coding Community

 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) {

int n = s.length(),len =0,maxlen =0;

stack<int> st;

st.push(-1);

for(int i =0;i<n;i++)

{

if(s[i] == '(')

st.push(i);

if(s[i] == ')')

{

st.pop();

if(st.empty())

st.push(i);

len = i - st.top();

maxlen = max(maxlen,len);

}

}

return maxlen;

}

};