백준 15650: N과 M (2) [JAVA]

https://www.acmicpc.net/problem/15650

 

 

[난이도]

- Silver 3

 

[알고리즘]

- 백트래킹

 

[코드]

import java.io.*;
import java.util.*;

public class Main {
    static int N, M;
    static boolean[] checked;
    static int[] arr;
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st = new StringTokenizer(br.readLine(), " ");

        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());
        checked = new boolean[N + 1];
        arr = new int[N + 1];
        backTracking(0, 1);
    }

    static void backTracking(int depth, int start) {
        if (depth == M) {
            for (int i = 0; i < M; i++) {
                System.out.print(arr[i] + " ");
            }
            System.out.println();
            return;
        }
        for (int i = start; i <= N; i++) {
            if (!checked[i]) {
                checked[i] = true;
                arr[depth] = i;
                backTracking(depth + 1, i + 1);
                checked[i] = false;
            }
        }
    }
}

 

[풀이]

for문을 돌때 시작을 i=1부터가 아닌 i=start부터 시작한다.