堆栈_括号匹配

class Solution {
public:
    bool isValid(string s) {
        if(s.empty())
            return false;
        stack<int> s1;
        int n=s.size();
        for(int i=0;i<n;i++)
        {
            if(s[i]==‘(‘||s[i]==‘[‘||s[i]==‘{‘)
                s1.push(s[i]);
            else if(s1.empty())
                return false;
            else if((s[i]==‘)‘&&s1.top()==‘(‘)||(s[i]==‘]‘&&s1.top()==‘[‘)||(s[i]==‘}‘&&s1.top()==‘{‘))
                s1.pop();
            else
                return false;
        }
        if(s1.empty())
            return true;
        else
            return false;
    }
};