กิจกรรมยามว่าง (activity)

Author: Pakin Olanraktham

Source: PROGRAMMING.IN.TH

Difficulty: ?

Prerequisites:

การเขียนโปรแกรมเบื้องต้น

เฉลย

CC++

#include <stdio.h>

long long nCr(int n, int r) {
    long long res = 1;

    for (int i = n; i > n-r; i--) res *= i;
    for (int i = r; i > 1; i--) res /= i;

    return res;
}

int main() {
    int n;
    scanf("%d", &n);

    printf("%lld\n", (n&1 == 1 ? 2*nCr(n, n/2) : nCr(n, n/2)));
}

#include <iostream>

using namespace std;

long long nCr(int n, int r) {
    long long res = 1;

    for (int i = n; i > n-r; i--) res *= i;
    for (int i = r; i > 1; i--) res /= i;

    return res;
}

int main() {
    int n;
    cin >> n;

    cout << (n&1 == 1 ? 2*nCr(n, n/2) : nCr(n, n/2)) << '\n';
}