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