有效的括號匹配

bool isValid(string s) {

    if(s.size() == 0)
      {
       return false;
      }
      stack<char>stackHelp;;
      for(int i = 0; i < s.length(); i ++)
      {
        if(s[i] == '(' || s[i] == '{' || s[i] == '[')
        {
          stackHelp.push(s[i]);
        }
        if(s[i] == ')' || s[i] == '}' || s[i] == ']')
        {
            if(stackHelp.empty())
            {
              return false;
            }

            if(s[i] == ')' && stackHelp.top() != '(')
            {
                return false;
            }
            if(s[i] == '}' && stackHelp.top() != '{')
            {
                return false;
            }

            if(s[i] == ']' && stackHelp.top() != '[')
            {
                return false;
            }

            stackHelp.pop();
        }



       }

      if(stackHelp.empty())
      {
        return true;
      }
      else
      {
        return false;
      }
 
    }