[Oracle] LeetCode 20 Valid Parentheses

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

• Open brackets must be closed by the same type of brackets.
• Open brackets must be closed in the correct order.
• Every close bracket has a corresponding open bracket of the same type.

Solution

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class Solution {
private:
    stack<char> sk1;
public:
    bool isValid(string s) {
        int n = s.size();
        if(n%2)return false;
        
        for(int i=0;i<n;i++){
            if(s[i]=='(' || s[i]=='[' || s[i]=='{')sk1.push(s[i]);
            else{
                if(!sk1.empty()){
                    auto f = sk1.top(); sk1.pop();
                    if(f=='('){
                        if(s[i]==')')continue;
                        else return false;
                    }
                    else if(f=='['){
                        if(s[i]==']')continue;
                        else return false;
                    }
                    else if(f=='{'){
                        if(s[i]=='}')continue;
                        else return false;
                    }
                }
                else return false;
                
            }
        }
        if(!sk1.empty())return false;
        return true;
    }
};