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:

 1 class Solution {

 2 public:

 3     bool isValid(string s) {

 4         int n=s.size();

 5         if(n%2==1)

 6             return false;

 7         stack<char> a;    //push,pop,top,size

 8          for(int i=0;i<n;i++){

 9             if(s[i]=='('|| s[i]=='['||s[i]=='{') 

10                 a.push(s[i]);

11             else if (a.empty()==false &&( (a.top()=='(' && s[i]==')') || (a.top()=='[' && s[i]==']') || (a.top()=='{' && s[i]=='}') ) )

12                 a.pop();

13             else 

14                 return false;

15          }

16          if(a.empty())

17             return true;

18          else return false;

19     }

20 };