poj2229Sumsets

http://poj.org/problem?id=2229

挺好的一公式。。

 1 #include <iostream>

 2 #include<cstdio>

 3 #include<cstring>

 4 #include<algorithm>

 5 #include<stdlib.h>

 6 using namespace std;

 7 #define  N 1000010

 8 #define mod 1000000000

 9 long long dp[N];

10 int a[N];

11 int main()

12 {

13     int i,j,k,n;

14     while(cin>>n)

15     {

16         memset(dp,0,sizeof(dp));

17         memset(a,0,sizeof(a));

18         dp[1] = 1;

19         dp[2] = 2;

20         dp[3] = 2;

21         dp[4] = 4;

22         for(i = 5; i <= n ; i++)

23         {

24             if(i%2!=0)

25             dp[i] = dp[i-1];

26             else

27             {

28                 dp[i] = (dp[i-2]+dp[i/2])%mod;

29             }

30         }

31         cout<<dp[n]%mod<<endl;

32     }

33     return 0;

34 }

View Code