【dp求期望值】POJ 3756

dp求期望

double dp[1024][111];//dp[i][j]第i round到j格的機率bool stop[111];int go[111];int n;int main(){    while(scanf("%d",&n) !=-1){        int i,j;        int m;        memset(go,0,sizeof(go));        memset(stop,0,sizeof(stop));        scanf("%d",&m);        while(m--){            int pos,num;            scanf("%d%d",&pos,&num);            go[pos]+=num;        }        scanf("%d",&m);        while(m--){            int pos,num;            scanf("%d%d",&pos,&num);            go[pos]-=num;        }        scanf("%d",&m);        while(m--){            int pos;            scanf("%d",&pos);            stop[pos] = true;        }        memset(dp,0,sizeof(dp));        dp[0][0] = 1.0;        double per = 1.0/6.0;        for(i=0;i<1000;i++){            for(j=0;j<n;j++){                if(dp[i][j]>0){                    for(int k=1;k<=6;k++){                        int next = k+j;                        if(next>n){                            int res = next%n;                            next = n-res;                        }                        if(stop[next]){                            dp[i+2][next] += dp[i][j]*per;                        } else {                            next += go[next];                            if(next>n){                                int res = next%n;                                next = n-res;                            } else if(next<0)next =-next;                            dp[i+1][next] += dp[i][j]*per;                        }                    }                }            }        }        double ans = 0;        for(i=0;i<1000;i++){            ans += dp[i][n]*i;        }        if(ans<eps)puts("Impossible");        else        printf("%.2lf\n",ans);    }    return 0;}