199. Stateful Lambda Counter

#include <iostream>
#include <string>
#include <functional>

class Ticker {
private:
    std::function<void()> callback;

public:
    void setCallback(std::function<void()> cb) {
        callback = cb;
    }

    void tick() {
        if (callback) callback();
    }
};

int main() {
    Ticker sys_tick;

    // TODO: Define a lambda that maintains state.
    // Hint: Use [count = 0]() mutable { ... }
    // The lambda should increment count and print:
    // "Count: " << count << std::endl;

    // sys_tick.setCallback(...);
    sys_tick.setCallback([count=0]()mutable{
        count++;
        std::cout<<"Count: " << count << std::endl;
    });
    int N;
    if (!(std::cin >> N)) return 0;

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

        if (cmd == "TICK") {
            sys_tick.tick();
        }
    }
    return 0;
}