leetcode Longest Valid Parentheses-优快云博客

本文探讨了如何在仅包含'('和')'的字符串中找到最长的有效括号子串长度。通过使用栈来记录左括号的位置，并利用布尔数组标记匹配的括号，最后遍历标记数组计算最长连续匹配子串的长度。

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题目连接

https://leetcode.com/problems/longest-valid-parentheses/

Longest Valid Parentheses

Description

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.

记录括号出现的位置，找连续最长的一段。。

class Solution {
public:
	int longestValidParentheses(string s) {
		if (s.empty()) return 0;
		int n = s.length();
		stack<int> st;
		vector<bool> vis(n + 10);
		for (int i = 0; i < n; i++) {
			char &c = s[i];
			if (c == '(') {
				st.push(i);
			} else if (c == ')' && !st.empty()){
				vis[i] = true;
				vis[st.top()] = true; st.pop();
			}
		}
		int ans = 0, ret = 0;
		for (int i = 0; i < n; i++) {
			if (vis[i]) ++ret;
			else ret = 0;
			ans = max(ans, ret);
		}
		return ans;
	}
};

转载于:https://www.cnblogs.com/GadyPu/p/5040184.html