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.

[b]******************************[/b]我是一条分割线[b]************************[/b]

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。