[LeetCode][Java] Longest Valid Parentheses

题目:

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.

题意:

给定一个字符串值包含字符‘(‘ and ‘)‘,找出最长有效括号子串。

对于 "(()",最长有效子串为"()",长度为2.

另一个例子是")()())",其中的最长有效括号子串为"()()",长度为4.

算法分析:

  1. stack里面装的一直是“还没配好对的那些可怜的括号的index”
  2. 是’(‘的时候push
  3. 是’)‘的时候,说明可能配对了;看stack top是不是左括号,不是的话,push当前右括号
  4. 是的话,pop那个配对的左括号,然后update res:i和top的(最后一个配不成对的)index相减,就是i属于的这一段的当前最长。如果一pop就整个栈空了,说明前面全配好对了,那res就是最大=i+1

AC代码:

public class Solution
{
    public int longestValidParentheses(String s)
    {
        int res = 0;
        Stack<Integer> stack = new Stack<Integer>();
        char[] arr = s.toCharArray();
        for (int i = 0; i < arr.length; i++)
        {
            if (arr[i] == ')' && !stack.isEmpty() && arr[stack.peek()] == '(')
            {
                stack.pop();
                if (stack.isEmpty())
                    res = i + 1;
                else
                    res = Math.max(res, i - stack.peek());
            }
            else
            {
                stack.push(i);
            }
        }
        return res;
    }
}

版权声明:本文为博主原创文章,转载注明出处

时间: 2024-11-05 18:35:22

[LeetCode][Java] Longest Valid Parentheses的相关文章

[LeetCode] 032. Longest Valid Parentheses (Hard) (C++)

指数:[LeetCode] Leetcode 指标解释 (C++/Java/Python/Sql) Github: https://github.com/illuz/leetcode 032. Longest Valid Parentheses (Hard) 链接: 题目:https://oj.leetcode.com/problems/longest-valid-parentheses/ 代码(github):https://github.com/illuz/leetcode 题意: 问一个字

leetcode 之 Longest Valid Parentheses

leetcode中和括号匹配相关的问题共有三个,分别是: Valid Parentheses Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the correct order, "()" and "()[]{}" are a

Java for LeetCode 032 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 &

LeetCode 32 Longest Valid Parentheses (C,C++,Java,Python)

Problem: 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 exa

Java [leetcode 32]Longest Valid Parentheses

题目描述: 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 exampl

【LeetCode】Longest Valid Parentheses 解题报告

[题目] 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

[LeetCode][JavaScript]Longest Valid Parentheses

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

LeetCode 之 Longest Valid Parentheses(栈)

[问题描写叙述] 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 exa

[LeetCode] 32. Longest Valid Parentheses 最长有效括号

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 &