题解

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 18;

int n,l,r,x,a[N];

int main(){
cin >> n >> l >> r >> x;
for(int i=0;i<n;i++){
cin >> a[i];
}

int ans = 0;
for(int mask=0; mask<(1<<n); mask++){
	if(__builtin_popcount(mask) < 2) continue;
	int sum=0, mi=INT_MAX, mx=0;
	for(int i=0; i<n; i++){
		if( mask & (1<<i)){
			sum += a[i];
			mi = min(mi, a[i]);
			mx = max(mx, a[i]);
		}
	}
	if(l<=sum && sum<=r && mx-mi>=x) ans++;
}
cout << ans;
return 0;

}