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.
1）stack<char>的数据结构，stk.push(elem),stk.pop(),stk.top等用法。
2）栈为空，输入为左括弧，输入为右括弧，分不同情况讨论，入栈，出栈，退出，continue等
class Solution {
public:原文地址：http://blog.csdn.net/shahongzhou/article/details/40383481
