这题嘛。。。不会
Orz 这个解答 P33开始 2333
1 /************************************************************** 2 Problem: 2318 3 User: rausen 4 Language: C++ 5 Result: Accepted 6 Time:0 ms 7 Memory:808 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <cmath> 12 #include <algorithm> 13 14 using namespace std; 15 typedef double lf; 16 const int N = 105; 17 int T, n; 18 lf p, q, k; 19 lf p1, p2, p3, p4; 20 lf p5, p6, p7, p8; 21 lf f[N], s[N]; 22 23 int main(){ 24 scanf("%d", &T); 25 int i; 26 while (T--){ 27 scanf("%d%lf%lf", &n, &p, &q); 28 f[0] = 0, s[0] = 1; 29 n = min(100, n); 30 k = 1 - (1 - p) * (1 - q); 31 p1 = p / k, p2 = (1 - p) * q / k; 32 p3 = (1 - q) * p / k, p4 = q / k; 33 k = 1 - p * q; 34 p5 = (1 - p) / k, p6 = (1 - q) * p / k; 35 p7 = q * (1 - p) / k, p8 = (1 - q) / k; 36 for (i = 1; i <= n; ++i) 37 if (f[i - 1] < s[i - 1]){ 38 f[i] = p1 * s[i - 1] + p2 * f[i - 1]; 39 s[i] = p3 * s[i - 1] + p4 * f[i - 1]; 40 } else{ 41 f[i] = p5 * s[i - 1] + p6 * f[i - 1]; 42 s[i] = p7 * s[i - 1] + p8 * f[i - 1]; 43 } 44 printf("%.6lf ", f[n]); 45 } 46 return 0; 47 }