DFS Codeforces Round #306 (Div. 2) B. Preparing Olympiad

题目传送门

 /*
     DFS: 排序后一个一个出发往后找，找到>r为止，比赛写了return ；
 */
 #include <cstdio>
 #include <iostream>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 #include <vector>
 #include <map>
 #include <queue>
 #include <set>
 #include <string>
 #include <stack>
 using namespace std;

 typedef long long ll;
 const int MAXN = 1e4 + ;
 const int INF = 0x3f3f3f3f;
 int a[];
 bool vis[];
 int n, l, r, x;
 int ans;

 void DFS(int sum, int cnt, int s, int p)
 {
     if (sum >= l && cnt >=  && a[p] - a[s] >= x)    ans++;
     for (int i=p+; i<=n; ++i)
     {
         if (sum + a[i] <= r)    DFS (sum + a[i], cnt + , s, i);
     }
 }

 int main(void)        //Codeforces Round #306 (Div. 2) B. Preparing Olympiad
 {
     while (scanf ("%d%d%d%d", &n, &l, &r, &x) == )
     {
         ans = ;
         for (int i=; i<=n; ++i)    scanf ("%d", &a[i]);
         sort (a+, a++n);
         for (int i=; i<n; ++i)    DFS (a[i], , i, i);
         printf ("%d\n", ans);
     }

     return ;
 }

 /*
 3 5 6 1
 1 2 3
 4 40 50 10
 10 20 30 25
 5 25 35 10
 10 10 20 10 20
 */