Baekjoon Algorithm | Problem 15650: N and M (2)

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Source

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

Problem

Solve Baekjoon Online Judge problem 15650, N and M (2).

Input

Follow the input format and constraints given in the original problem statement.

Output

Print the answer required by the problem.

Sample Input 1

3 1

Sample Output 1

1 2 3

Sample Input 2

4 2

Sample Output 2

1 2 1 3 1 4 2 3 2 4 3 4

Sample Input 3

4 4

Sample Output 3

1 2 3 4

Algorithm Classification

  • Backtracking

Solution

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {

    static StringBuilder sb = new StringBuilder();
    static int n, m;
    static int[] arr;

    public static void main(String[] args) throws IOException {
        try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
            StringTokenizer input = new StringTokenizer(br.readLine(), " ");
            n = Integer.parseInt(input.nextToken());
            m = Integer.parseInt(input.nextToken());
        }

        arr = new int[m];
        dfs(0, 1);
        System.out.println(sb);
    }

    /**
     * Depth-first search (DFS)
     */
    static void dfs(int depth, int start) {
        if (depth == m) {
            for (int value : arr) {
                sb.append(value).append(" ");
            }
            sb.append("\n");
            return;
        }
        for (int i = start; i <= n; i++) {
            arr[depth] = i;
            dfs(depth + 1, i + 1);
        }
    }
}