**(leetcode_string) Valid Parentheses

Valid Parentheses

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Question Solution 

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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利用stack~！

class Solution {public:    bool isValid(string s) {        stack<char> stk;        int i;        for(i=0;i<s.length();i++){            if(s[i]=='(' || s[i]=='[' || s[i]=='{')                stk.push(s[i]);            else{                if(!stk.empty()&&((stk.top()=='('&&s[i]==')') ||(stk.top()=='['&&s[i]==']')||(stk.top()=='{'&&s[i]=='}')))                        stk.pop();                else                    return false;            }        }        return stk.empty();    }};