【BZOJ2318】【SPOJ4060】Game with Probability Problem

#include<bits/stdc++.h>
using namespace std;
#define MAXN	5005
#define DONE	1000
double f[MAXN], g[MAXN];
int main() {
int T;
scanf("%d", &T);
while (T--) {
int n;
double p, q;
scanf("%d%lf%lf", &n, &p, &q);
n = min(n, DONE);
double tmp = p + q - p * q;
f[1] = p / tmp; g[1] = q / tmp;
for (int i = 2; i <= n; i++) {
double tmp, ans, bns;
f[i] = 0;
tmp = p;
ans = (p * (1 - g[i - 1]) + (1 - p) * q * f[i - 1]) / (p + q - p * q);
bns = (p * (1 - g[i - 1]) + (1 - p) * (1 - q) * f[i - 1]) / (1 - q + p * q);
f[i] = max(f[i], min(ans, bns));
p = 1 - p;
ans = (p * (1 - g[i - 1]) + (1 - p) * q * f[i - 1]) / (p + q - p * q);
bns = (p * (1 - g[i - 1]) + (1 - p) * (1 - q) * f[i - 1]) / (1 - q + p * q);
f[i] = max(f[i], min(ans, bns));
p = tmp;
g[i] = 0;
tmp = q;
ans = (q * (1 - f[i - 1]) + (1 - q) * p * g[i - 1]) / (p + q - p * q);
bns = (q * (1 - f[i - 1]) + (1 - q) * (1 - p) * g[i - 1]) / (1 - p + p * q);
g[i] = max(g[i], min(ans, bns));
q = 1 - q;
ans = (q * (1 - f[i - 1]) + (1 - q) * p * g[i - 1]) / (p + q - p * q);
bns = (q * (1 - f[i - 1]) + (1 - q) * (1 - p) * g[i - 1]) / (1 - p + p * q);
g[i] = max(g[i], min(ans, bns));
q = tmp;
}
printf("%.6lf\n", f
);
}
return 0;
}