【Leetcode】

问题描述

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 all valid but "(]" and "([)]" are not.

括号配对问题，而且还只输入括号，用一个栈就可以了

代码

class Solution {	
public:
    bool isValid(string s) {
        stack<char> r;
        if(s.length()<1) 
			return true;
        r.push(s[0]);
        for(int i=1;i<s.length();i++) {
        	if(r.size()>0&&(s[i]==')'&&r.top()=='('
				|| s[i]==']'&&r.top()=='['
				|| s[i]=='}'&&r.top()=='{')) {
	        	r.pop();
	        } else {
				r.push(s[i]);
        	}
        }
        if(r.size()>0) 
			return false;
        return true;
    }
};