OJ-Problems-Source/HDOJ/4487_autoAC.cpp

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#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>
#define LL long long
#define CLR(a, b) memset(a, b, sizeof(a))
using namespace std;
const int N = 205;
double dp[2][N][N];
int main()
{
int t, n,cas;double L, R, ans;
scanf("%d", &t);
while(t --)
{
scanf("%d%d%lf%lf", &cas, &n, &L, &R);
CLR(dp, 0);dp[0][0][100] = 1;
for(int i = 1; i <= n; i ++)
{
CLR(dp[i&1], 0);
for(int j = 0; j <= i; j ++)
{
for(int k = 100 - i; k <= 100 + j; k ++)
{
dp[i&1][j][k] += dp[(i-1)&1][j][k-1] * R;
dp[i&1][j][k] += dp[(i-1)&1][j][k+1] * L;
dp[i&1][j][k] += dp[(i-1)&1][j][k] * (1.0 - L - R);
}
dp[i&1][j][100+j] += dp[(i-1)&1][j-1][99+j] * R;
}
}ans = 0;
for(int i = 0; i <= n; i ++)
{
for(int j = 100 - n; j <= 100 + n; j ++)
{
ans += i * dp[n&1][i][j];
}
}
printf("%d %.4lf\n", cas, ans);
}
}