华为OD机考-小明减肥-DFS（JAVA 2025B卷）

import java.util.*;
public class XiaomingLoseWeight {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int[] ints = Arrays.stream(scanner.nextLine().split("\\s+")).mapToInt(Integer::parseInt).toArray();
        int n=ints[0],t=ints[1],k=ints[2];
        int[] arrs = Arrays.stream(scanner.nextLine().split("\\s+")).mapToInt(Integer::parseInt).toArray();
        int[] used = new int[n];
        Arrays.sort(arrs);
        dfs(arrs,used,0,t,k);
        System.out.println(cnt);

    }
    private static int cnt = 0;

    private static void dfs(int[] arrs,int[] used ,int start, int t, int k) {
        if(t==0 && k==0){
            cnt++;
        }
        for (int i = start; i < arrs.length; i++) {
            if(i<arrs.length-1&& arrs[i+1]==arrs[i]&&used[i]==0){
                continue;
            }
            used[i] = 1;
            dfs(arrs,used,start+1,t-arrs[i],k-1);
            used[i]=0;
        }
    }
}