HDU 5781 ATM Mechine

概率DP。

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<iostream>
using namespace std;
typedef long long LL;
const double pi=acos(-1.0),eps=1e-8;
void File()
{
    freopen("D:\\in.txt","r",stdin);
    freopen("D:\\out.txt","w",stdout);
}
inline int read()
{
    char c = getchar();  while(!isdigit(c)) c = getchar();
    int x = 0;
    while(isdigit(c)) { x = x * 10 + c - ‘0‘; c = getchar(); }
    return x;
}

double dp[2010][20];

void init()
{
    for(int i=1;i<=2000;i++) for(int j=0;j<=15;j++) dp[i][j]=999999;
    for(int i=0;i<=15;i++) dp[0][i]=0;
    for(int i=1;i<=2000;i++)
        for(int j=1;j<=15;j++)
            for(int x=1;x<=i;x++)
                dp[i][j]=min(dp[i][j],1.0*(i-x+1)/(i+1)*dp[i-x][j]+1.0*x/(i+1)*dp[x-1][j-1]+1);
}

int main()
{
    int w,k;init();
    while(~scanf("%d%d",&w,&k))
    {
        printf("%.6lf\n",dp[w][min(k,15)]);
    }
    return 0;
}