Fibonacci Memoization

#include <bits/stdc++.h>
#define ll long long

using namespace std;

ll f[51];
bool calced[51];

ll fib(int n) {
    if (n <= 1) {
        return n;
    } else if (calced[n]) {
        return f[n];
    } else {
        f[n] = fib(n - 2) + fib(n - 1);
        calced[n] = true;
        return f[n];
    }
}

int main() {
    std::ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n;
    cin >> n;
    cout << fib(n);
    return 0;
}