hdu 5366 组合数 *

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<cmath>
 6 #include<queue>
 7 #include<map>
 8 using namespace std;
 9 #define MOD 1000000007
10 const int INF=0x3f3f3f3f;
11 const double eps=1e-5;
12 typedef long long ll;
13 #define cl(a) memset(a,0,sizeof(a))
14 #define ts printf("*****\n");
15 const int MAXN=1005;
16 int n,m,tt;
17 ll c[MAXN][MAXN];
18 
19 void init()     //初始化组合数
20 {
21     c[0][0]=c[1][0]=c[1][1]=1;
22     for(int i=2;i<=62;i++)
23     {
24         c[i][0]=1;
25         for(int j=1;j<i;j++)
26             c[i][j]=c[i-1][j]+c[i-1][j-1];
27         c[i][i]=1;
28     }
29 }
30 int main()
31 {
32     int i,j,k,ca=1;
33     #ifndef ONLINE_JUDGE
34     freopen("1.in","r",stdin);
35     #endif
36     init();
37     while(scanf("%d",&n)!=EOF)
38     {
39         int r=1;
40         ll sum=0;
41         while(n-3*(r-1)-1+r>0)
42         {
43             sum+=c[n-3*(r-1)-1+r][r];
44             r++;
45         }
46         printf("%I64d\n",sum);
47     }
48 }