day11

class Solution {
public:
 bool isValid(string s) {
 if (s.empty())
 return true;
stack<char> sk;
  unordered_map<char, char> m = {{')', '('}, {']', '['}, {'}', '{'}};
for (char& c : s) {
 if (c == '(' || c == '[' || c == '{')
 sk.push(c);
if (c == ')' || c == ']' || c == '}') 
{ if (!sk.empty() && sk.top() == m[c])
 sk.pop();
  else
                    return false;
  }
        }
 return sk.empty();
    }
};