50014. Selection

#include <stdio.h>
#include <stdlib.h>
#include "subset.h"
 
int cmp(const void* a, const void* b){
    return (*(int*)a - *(int*)b);
}
 
int solve(int* arr, int now_idx, int n, int k, int s){
    if(s == 0 && k == 0){
        return 1;
    }
    else if(k < 0 || s < 0 || n == now_idx || n - now_idx < s){
        return 0;
    }
    else{
        int pick =     solve(arr, now_idx + 1, n, k - arr[now_idx], s - 1);
        if(pick) return pick;
        int not_pick = solve(arr, now_idx + 1, n, k               , s    );
        if(not_pick) return not_pick;
        return 0;
     }
}
 
int subset(int numbers[], int n, int K, int S){
    qsort(numbers, n, sizeof(int), cmp);
    int i;
    for(i = 0; i < n; i++) if(numbers[i] > K) break;
    return solve(numbers, 0, i, K, S);
}

#include <stdlib.h>
#include "subset.h"

int subset(int arr[], int n, int k, int s){
    if(k == 0 && s == 0){
        return 1;
    }
    else if(k < 0 || s < 0 || n == 0 || s > n){
        return 0;
    }
    else{
        return subset(arr + 1, n - 1, k - arr[0], s - 1) || subset(arr + 1, n - 1, k, s);
    }
}