BZOJ2318 Spoj4060 game with probability Problem

这题嘛。。。不会

Orz 这个解答 P33开始 2333

/**************************************************************
    Problem: 2318
    User: rausen
    Language: C++
    Result: Accepted
    Time:0 ms
    Memory:808 kb
****************************************************************/
 
#include <cstdio>
#include <cmath>
#include <algorithm>
 
using namespace std;
typedef double lf;
const int N = 105;
int T, n;
lf p, q, k;
lf p1, p2, p3, p4;
lf p5, p6, p7, p8;
lf f[N], s[N];
 
int main(){
    scanf("%d", &T);
    int i;
    while (T--){
        scanf("%d%lf%lf", &n, &p, &q);
        f[0] = 0, s[0] = 1;
        n = min(100, n);
        k = 1 - (1 - p) * (1 - q);
        p1 = p / k, p2 = (1 - p) * q / k;
        p3 = (1 - q) * p / k, p4 = q / k;
        k = 1 - p * q;
        p5 = (1 - p) / k, p6 = (1 - q) * p / k;
        p7 = q * (1 - p) / k, p8 = (1 - q) / k;
        for (i = 1; i <= n; ++i)
            if (f[i - 1] < s[i - 1]){
                f[i] = p1 * s[i - 1] + p2 * f[i - 1];
                s[i] = p3 * s[i - 1] + p4 * f[i - 1];
            } else{
                f[i] = p5 * s[i - 1] + p6 * f[i - 1];
                s[i] = p7 * s[i - 1] + p8 * f[i - 1];
            }
        printf("%.6lf
", f[n]);
    }
    return 0;
}