fzu 2037 Maximum Value Problem

http://acm.fzu.edu.cn/problem.php?pid=2037

思路：找规律，找出递推公式f[n]=f[n-1]*n+(n-1)!,另一个的结果也是一个递推，s[n]=s[n-1]+1/n;

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <algorithm>

 4 #define maxn 1000010

 5 #define ll long long

 6 using namespace std;

 7 const int mod=1000000007;

 8 

 9 ll f[maxn];

10 int t;

11 ll n;

12 ll h[maxn];

13 double ans[maxn];

14 

15 void inti()

16 {

17     h[0]=1;

18     h[1]=1;

19     ans[1]=1.0;

20     for(int i=2; i<=maxn; i++)

21     {

22         ans[i]=ans[i-1]+1.0/i;

23         h[i]=h[i-1]*i;

24         h[i]%=mod;

25     }

26     f[1]=1;

27     for(int i=2; i<=maxn; i++)

28     {

29          f[i]=(f[i-1]*i+h[i-1])%mod;

30     }

31 }

32 

33 int main()

34 {

35     inti();

36     scanf("%d",&t);

37     for(int cas=1; cas<=t; cas++)

38     {

39         scanf("%lld",&n);

40         printf("Case %d: %I64d %.6lf\n",cas,f[n],ans[n]);

41     }

42     return 0;

43 }

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