leetcode-20-字符串题-有效的括号

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题目

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解法

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class Solution {
public:
    bool isValid(string s) {
        if(s.empty()) return true;

        stack<char> help;
        for(auto x : s){
            if(x == '(' || x == '[' || x == '{'){
                help.push(x);
            }else{
                if(!help.empty()){
                    if(x == ')' && help.top() == '('){
                        help.pop();
                    }else if(x == ']' && help.top() == '['){
                        help.pop();
                    }else if(x == '}' && help.top() == '{'){
                        help.pop();
                    }else{
                        return false;
                    }
                }else{
                    return false;
                }
            }
        }

        return help.empty() ? true : false;
    }
};