递推DP URAL 1260 Nudnik Photographer

题目传送门

 1 /*
 2     递推DP: dp[i] 表示放i的方案数，最后累加前n-2的数字的方案数
 3 */
 4 #include <cstdio>
 5 #include <algorithm>
 6 #include <cmath>
 7 #include <cstring>
 8 using namespace std;
 9
10 const int MAXN = 1e4 + 10;
11 const int INF = 0x3f3f3f3f;
12 int dp[60];
13
14 int main(void)        //URAL 1260 Nudnik Photographer
15 {
16     //freopen ("G.in", "r", stdin);
17
18     int n;
19     while (scanf ("%d", &n) == 1)
20     {
21         memset (dp, 0, sizeof (dp));
22         dp[1] = 1;
23         for (int i=2; i<=n; ++i)
24         {
25             dp[i] = dp[i-1];
26             if (i > 3)
27             {
28                 dp[i] += dp[i-3];
29             }
30         }
31
32         long long ans = dp[n];
33         if (n > 2)
34         {
35             for (int i=1; i<=n-2; ++i)    ans += dp[i];
36         }
37         printf ("%I64d\n", ans);
38     }
39
40     return 0;
41 }