CodeForces 540D Bad Luck Island 概率dp

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define db double
const int maxn=108;
db dp[maxn][maxn][maxn];
int main()
{
int i,j,n,m,k,p;
while(scanf("%d%d%d",&n,&m,&k)==3)
{
memset(dp,0,sizeof(dp));
dp
[m][k]=1.0;
for(i=n;i>=1;i--)
for(j=m;j>=1;j--)
for(p=k;p>=1;p--)
{
db shit=i*j+j*p+i*p;
dp[i-1][j][p]+=dp[i][j][p]*(i*p*1.0/shit);
dp[i][j-1][p]+=dp[i][j][p]*(i*j*1.0/shit);
dp[i][j][p-1]+=dp[i][j][p]*(j*p*1.0/shit);
}
db x,y,z;
x=y=z=0.0;
for(i=1;i<=100;i++)
for(j=0;j<=100;j++)
{
x+=dp[i][j][0];
y+=dp[0][i][j];
z+=dp[j][0][i];
}
printf("%.10f %.10f %.10f\n",x,y,z);
}
return 0;
}