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

 1 /*
 2     DFS: 排序后一个一个出发往后找，找到>r为止，比赛写了return ；
 3 */
 4 #include <cstdio>
 5 #include <iostream>
 6 #include <cstring>
 7 #include <cmath>
 8 #include <algorithm>
 9 #include <vector>
10 #include <map>
11 #include <queue>
12 #include <set>
13 #include <string>
14 #include <stack>
15 using namespace std;
16 
17 typedef long long ll;
18 const int MAXN = 1e4 + 10;
19 const int INF = 0x3f3f3f3f;
20 int a[20];
21 bool vis[20];
22 int n, l, r, x;
23 int ans;
24 
25 void DFS(int sum, int cnt, int s, int p)
26 {
27     if (sum >= l && cnt >= 2 && a[p] - a[s] >= x)    ans++;
28     for (int i=p+1; i<=n; ++i)
29     {
30         if (sum + a[i] <= r)    DFS (sum + a[i], cnt + 1, s, i);
31     }
32 }
33 
34 int main(void)        //Codeforces Round #306 (Div. 2) B. Preparing Olympiad
35 {
36     while (scanf ("%d%d%d%d", &n, &l, &r, &x) == 4)
37     {
38         ans = 0;
39         for (int i=1; i<=n; ++i)    scanf ("%d", &a[i]);
40         sort (a+1, a+1+n);
41         for (int i=1; i<n; ++i)    DFS (a[i], 1, i, i);
42         printf ("%d
", ans);
43     }
44 
45     return 0;
46 }
47 
48 /*
49 3 5 6 1
50 1 2 3
51 4 40 50 10
52 10 20 30 25
53 5 25 35 10
54 10 10 20 10 20
55 */
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