dsa-competitive-programming/leetcode/lc20/OptimalParantheses.cpp

class Solution{
    public:
        bool isValid(string s){
            stack<char> st;
            for(char c : s){
                if(c=='(' || c == '{' || c == '[') st.push(c);
                else{
                    if(st.empty()) return false;

                    char top = st.top();
                    st.pop();

                    if((c==')' && top!='(') || (c == '}' && top!= '{') || (c == ']' && top!= '[')) return false;
                }
            }
            return st.empty();
        }
};