[Leetcode] [Java] Longest Valid parentheses

Title:

Given A string containing just the characters ‘(‘ ‘)‘ and, find the length of the longest valid (well-formed) parenthe SES substring.

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

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

Test Instructions:

given a string value containing the character " ('  AND  ", Find the longest valid brace substring.

< Span style= "Background-color:rgb (255,255,255)" for &NBSP; " (() " , the longest valid substring is " () ", length 2.

< Span style= "Font-family:menlo,monaco,consolas, ' Courier New ', monospace; line-height:30px ">< Span style= "Background-color:rgb (255,255,255)" and another example is " () ()) ", where the longest valid brace substring is " () () ", length 4.

Algorithm Analysis:

1. The stack is always "index of poor brackets that are not well-fitted"
2. Is ' (' when the push
3. Is ') ', the explanation may be paired; see if Stack top is an opening parenthesis, or not, push the current closing parenthesis
4. Yes, pop that paired left parenthesis, and then update res:i and top (the last mismatched) index minus, which is the current longest of the section I belongs to. If a pop on the entire stack empty, the front is fully equipped with the right, that Res is the largest =i+1

AC Code:

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;    }}

Copyright NOTICE: This article is the original article of Bo Master, reprint annotated source

[Leetcode] [Java] Longest Valid parentheses