백준 s3 15649 N과 M (1) c++

https://www.acmicpc.net/problem/15649

 

/*boj s3 15649 N과 M (1)*/
#include <iostream>
#define MAXN 9
using namespace std;

int N, M;
int answer[MAXN];
bool isUsed[MAXN];

void func(int k) {
    if (k == M) {
        for (int i = 0; i < M; i++) {
            cout << answer[i] << " ";
        }
        cout << '\n';
        return;
    }

    for (int i = 1; i <= N; i++) {
        if (isUsed[i]) continue;

        isUsed[i] = true;
        answer[k] = i;
        func(k + 1);

        isUsed[i] = false;
    }
}

int main(void) {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cin >> N >> M;

    func(0);
}

 

 

next_permutation 쓴 경우

do {
	순열 출력
} while(next_permutation(arr, arr+n);

 

 

 

/*s3 15649 N과M(1)_next_perm*/

#include <bits/stdc++.h>
#define MAX 10

using namespace std;

int n, m;
int arr[MAX];

int fac(int n) {
	if (n == 0) return 1;
	if (n == 1) return 1;
	return n * fac(n - 1);
}


int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	cin >> n >> m;

	for (int i = 0; i < n; i++) {
		arr[i] = i + 1;
	}

	int alt = fac(n - m) - 1; // 건너뛸 개수

	int cnt = alt;
	do {
		if (cnt == 0) {
			for (int i = 0; i < m; i++) {
				cout << arr[i] << " ";
			}
			cout << "\n";

			cnt = alt;
			continue;
		}
		cnt--;
	} while (next_permutation(arr, arr + n));

}