42 lines
1.1 KiB
C++
42 lines
1.1 KiB
C++
#include<iostream>
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#include<cstdio>
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#include<algorithm>
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#include<cstring>
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#include<cmath>
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#define eps 1e-10
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#define N (1<<7)+5
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#define inf 1<<20
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#define zero(a) (fabs(a)<eps)
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#define lson (step<<1)
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#define rson (step<<1|1)
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using namespace std;
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double p1,p2,p3,p4,p21,p31,p41;
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double dp[2005][2005],c[2005];
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int n,m,k;
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int main(){
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while(scanf("%d%d%d%lf%lf%lf%lf",&n,&m,&k,&p1,&p2,&p3,&p4)!=EOF){
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if(zero(p4)) {puts("0.00000");continue;}
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p21=p2/(1-p1);
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p31=p3/(1-p1);
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p41=p4/(1-p1);
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dp[1][1]=p4/(1-p1-p2);
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for(int i=2;i<=n;i++){
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for(int j=2;j<=(i<k?i:k);j++)
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c[j]=dp[i-1][j-1]*p31+p41;
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for(int j=k+1;j<=i;j++)
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c[j]=dp[i-1][j-1]*p31;
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double p=1,tmp=0;
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for(int j=i;j>1;j--){
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tmp+=p*c[j];
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p*=p21;
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}
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dp[i][i]=(tmp+p*p41)/(1-p*p21);
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dp[i][1]=p21*dp[i][i]+p41;
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for(int j=2;j<i;j++)
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dp[i][j]=p21*dp[i][j-1]+c[j];
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}
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printf("%.5f\n",dp[n][m]);
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}
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return 0;
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}
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