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

    解题思路:

    本题方法多多,是Java for LeetCode 020 Valid Parentheses题目的延续,因此,我们继续用栈的思路解决这个问题,其中需要一个index来维护最后一个')'出现的位置。JAVA代码如下:

    static public int longestValidParentheses(String s) {
    		int maxLength = 0,index=-1;
    		Stack<Integer> stack = new Stack<Integer>();
    		for (int i = 0; i < s.length(); i++) {
    			if (s.charAt(i) == '(')
    				stack.push(i);
    			else {
    				if(stack.empty())
    					index=i;
    				else{
    					stack.pop();
    					if(stack.isEmpty())
    						maxLength = Math.max(maxLength, i - index);
    					else maxLength=Math.max(maxLength, i - stack.peek());
    				}	
    			}
    		}
    		return maxLength;
    	}
    
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  • 原文地址:https://www.cnblogs.com/tonyluis/p/4485849.html
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