LeetCode题解(20)--Valid Parentheses

https://leetcode.com/problems/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.

思路:

考察stack的应用。

我的AC代码:

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