找规律 2015百度之星资格赛 1001 大搬家

 1 /*
 2     找规律：题目真心读不懂，排列组合的题目
 3 */
 4 #include <cstdio>
 5 #include <iostream>
 6 #include <algorithm>
 7 #include <cstring>
 8 using namespace std;
 9 
10 typedef long long ll;
11 
12 const int MAXN = 1e6 + 10;
13 const int INF = 0x3f3f3f3f;
14 const int MOD = 1e9 + 7;
15 ll dp[MAXN];
16 
17 void solve(void)
18 {
19     dp[1] = 1;    dp[2] = 2;
20     for (int i=3; i<=1e6; ++i)
21     {
22         dp[i] = (dp[i-1] + (i - 1) * dp[i-2]) % MOD;
23     }
24 }
25 
26 int main(void)        //2015百度之星资格赛 1001 大搬家
27 {
28     solve ();
29     int t, cas = 0;
30     scanf ("%d", &t);
31     while (t--)
32     {
33         int n;    scanf ("%d", &n);
34         printf ("Case #%d:\n", ++cas);
35         printf ("%I64d\n", dp[n]);
36     }
37 
38     return 0;
39 }
40 
41 
42 /*
43 2
44 1
45 3
46 */