leetcode之20. Valid Parentheses

原题：
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.
******************************我是一条分割线************************

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

};

头文件有一个#include ，是C++自带的栈，用起来还是很方便的。