Check for balanced parentheses using stack = () true ([)] false

BalancedParentheses.cpp

// https://www.youtube.com/watch?v=QZOLb0xHB_Q&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=18

#include <iostream>
#include <stack>
#include <string>

bool testBalance(std::string str) {
    std::stack<char> expressions;
    for (int i = 0; i < str.size(); i++) {
        char current = str[i];
        if (current == '{' || current == '[' || current == '(') {
            expressions.push(current);
            continue;
        }
        if (current == '}' || current == ']' || current == ')') {
            if (expressions.empty()) {
                return false;
            } else {
             // Compare the match
                char last = expressions.top();
                bool congruent = false;
                switch (last) {
                    case '{':
                        if (current == '}')
                            congruent = true;
                        break;
                    case '[':
                        if (current == ']')
                            congruent = true;
                        break;
                    case '(':
                        if (current == ')')
                            congruent = true;
                        break;
                    default:
                        break;
                }
                if (congruent) {
                    expressions.pop();
                } else {
                    return false;
                }
            }
        }
    }
    return expressions.empty();
};

int main() {
    std::string str;
    getline(std::cin, str);
    std::cout << testBalance(str) << std::endl;
    return 0;
}