[leetcode]Longest Valid Parentheses

用charAt()一直超时 改成char array竟然过了...

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