Configurable Math Engine

#include <iostream>
#include <string>

// TODO: Define a typedef 'MathOp' for a function pointer returning int, taking (int, int)
// typedef ... MathOp ...; 
// OR: using MathOp = ...;
using MathOp =  int (*)(int,int);
int add(int a, int b) { return a + b; }
int multiply(int a, int b) { return a * b; }

class Calculator {
private:
    // TODO: Declare member variable 'current_op' of type MathOp
    // Initialize it to 'add'
    MathOp current_op;
    
public:
    Calculator():current_op(add){}
    // TODO: Implement setMode
    void setMode(MathOp op) { current_op = op; }

    void compute(int a, int b) {
        // TODO: Call the function pointer
        // int res = ...
        // std::cout << "Result: " << res << std::endl;
        int res = current_op(a,b);
        std::cout << "Result: " << res << std::endl;
    }
};

int main() {
    Calculator calc;
    int N;
    if (!(std::cin >> N)) return 0;

    for (int i = 0; i < N; ++i) {
        std::string cmd;
        std::cin >> cmd;

        if (cmd == "MODE_ADD") {
            calc.setMode(add);
        } else if (cmd == "MODE_MUL") {
            calc.setMode(multiply);
        } else if (cmd == "CALC") {
            int a, b;
            std::cin >> a >> b;
            calc.compute(a, b);
        }
    }
    return 0;
}

Solving Approach