Longest Valid Parentheses

32. Longest Valid Parentheses

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.

For "(()", the longest valid parentheses substring is "()", which has length = 2.

Another example is ")()())", where the longest valid parentheses substring is "()()", which has length = 4.

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 (E) Valid Parentheses

 

class Solution {
public:
    int longestValidParentheses(string s) {
        int sSize  = s.size();
        int maxLen = 0;
        int start  = -1,end = 0;
        
        vector<int> matches(sSize,-1);//每个字符的匹配情况，字符为'('是值为-1,字符为')'时，值为其匹配的左括号的位置
        stack<int> stk;//左括号的位置
        
        for(int i=0;i<sSize;i++){
            if(s[i]=='('){
                stk.push(i);
                continue;
            }
            if(!stk.empty()){
                start      = stk.top();
                end        = i+1;                    
                matches[i] = start;//与i这个位置发生匹配的字符的位置是node.index
                while(start>0 && matches[start-1]!=-1){
                    start = matches[start-1];
                }
                maxLen = max(maxLen,end-start);        
                stk.pop();
            }
        }
        return maxLen;
    }
};
/**
(()(()))
 */