#include <string>
#include <stack>

class Solution
{
public:
    bool isValid(std::string s)
    {
        std::stack<char> open;

        for (char ch : s)
        {
            if (ch == '(' || ch == '{' || ch == '[')
            {
                open.push(ch);
            }
            else
            {
                if (open.empty())
                    return false;

                if ((open.top() == '(' && ch == ')') ||
                    (open.top() == '{' && ch == '}') ||
                    (open.top() == '[' && ch == ']'))
                {
                    open.pop();
                    continue;
                }
                return false;
            }
        }

        return open.empty();
    }
};