UVA 11021 C - Tribles(概率DP)

记忆化就可以搞定，比赛里都没做出来，真的是态度有问题啊。。。

 1 #include <iostream>

 2 #include<cstdio>

 3 #include<cstring>

 4 #include<algorithm>

 5 using namespace std;

 6 double p[1001];

 7 double dp[1001];

 8 int flag[1001],n;

 9 double po(double a,int k)

10 {

11     double b = 1.0;

12     while(k)

13     {

14         if(k&1)

15         b = a*b;

16         a = a*a;

17         k = k/2;

18     }

19     return b;

20 }

21 double dfs(int step)

22 {

23     int i;

24     if(flag[step])

25     return dp[step];

26     if(step == 1)

27     return p[0];

28     double ans = p[0],temp;

29     for(i = 1;i < n;i ++)

30     {

31         temp = p[i];

32         temp *= po(dfs(step-1),i);

33         ans += temp;

34     }

35     flag[step] = 1;

36     return dp[step] = ans;

37 }

38 int main()

39 {

40     int t,cas = 1,i,m,k;

41     double ans,temp;

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

43     while(t--)

44     {

45         scanf("%d%d%d",&n,&k,&m);

46         memset(flag,0,sizeof(flag));

47         for(i = 0;i < n;i ++)

48         scanf("%lf",&p[i]);

49         if(m == 0)

50         {

51             printf("Case #%d: %.7lf\n",cas++,0.0);

52             continue;

53         }

54         ans = 1;

55         temp = dfs(m);

56         for(i = 0;i < k;i ++)

57         ans *= temp;

58         printf("Case #%d: %.7lf\n",cas++,ans);

59     }

60     return 0;

61 }