Valid Parentheses

Problem

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.

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Idea

依次检查string的每个字符，如果是（，{,[则压入堆栈，如果是),{,]则弹出栈顶元素，并检查是否匹配。

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Note

如何遍历string里每个元素

string里的find

c++ Stack 用法

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Solution

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