(LeetCode)Longest Valid Parentheses

动态规划实现:

int longestValidParentheses(string s) {        if(s.length() <= 1) return 0;        int curMax = 0;        vector<int> longest(s.size(),0);        for(int i=1; i < s.length(); i++){            if(s[i] == ')' && i-longest[i-1]-1 >= 0 && s[i-longest[i-1]-1] == '('){                    longest[i] = longest[i-1] + 2 + ((i-longest[i-1]-2 >= 0)?longest[i-longest[i-1]-2]:0);                    curMax = max(longest[i],curMax);            }        }        return curMax;    }

用堆栈实现的:

 public int longestValidParentheses(String s) {       Stack<Integer> stack = new Stack();        boolean []end = new boolean[s.length()];        for(int i = 0; i < s.length() ; i ++)            end[i] = false;        for(int i = 0 ; i < s.length() ; i ++)        {            if(s.charAt(i) == '(')                stack.push(i);            else if(!stack.isEmpty())                end[stack.pop()] = end[i] = true;        }        int nowsum = 0,maxsum = 0;        for(int i = 0 ; i < s.length() ; i ++)        {            if(end[i] == false)                nowsum = 0;            else{                nowsum ++;                if(nowsum > maxsum)                    maxsum = nowsum;            }        }        return maxsum;    }