백준 1182번 부분수열의 합 [ Java ]

1182번: 부분수열의 합

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

public class Main {
    static int n, s, r;
    static int[] num;
    static int[] arr;
    static boolean[] visited;
    static int count = 0;
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        n = Integer.parseInt(st.nextToken());
        s = Integer.parseInt(st.nextToken());
        arr = Arrays.stream(br.readLine().split(" "))
                    .mapToInt(Integer::parseInt)
                    .toArray();
        visited = new boolean[n];
        for (int i=1; i<=n; i++){
            r = i;
            num = new int[r];
            bt(0, 0);
        }
        System.out.print(count);
    }
    static void bt(int depth, int start){
        if (depth == r){
            if (Arrays.stream(num).sum() == s) count++;
            return;
        }
        for (int i=start; i<arr.length; i++){
            if (!visited[i]){
                visited[i] = true;
                num[depth] = arr[i];
                bt(depth+1, i+1);
                visited[i] = false;
            }
        }
    }
}