题目链接
http://acm.hdu.edu.cn/showproblem.php?pid=5816
大牛的链接：
http://www.cnblogs.com/WABoss/p/5754721.html
1 #include <algorithm> 2 #include <iostream> 3 #include <cstring> 4 #include <cstdlib> 5 #include <cstdio> 6 #include <vector> 7 #include <ctime> 8 #include <queue> 9 #include <list> 10 #include <set> 11 #include <map> 12 using namespace std; 13 #define INF 0x3f3f3f3f 14 typedef long long LL; 15 16 LL fact[25], dp[1 << 20]; 17 int x[25]; 18 int main() 19 { 20 int t, p, n, m; 21 fact[0] = 1; 22 for(int i = 1; i <= 20; i++) 23 fact[i] = fact[i - 1] * i; 24 scanf("%d", &t); 25 while(t--) 26 { 27 scanf("%d %d %d", &p, &n, &m); 28 int N = n + m; 29 for(int i = n; i < N; i++) 30 scanf("%d", x + i); 31 memset(dp, 0, sizeof(dp)); 32 dp[0] = 1; 33 for(int i = 0; i < (1 << N); i++) 34 { 35 if(dp[i] == 0) 36 continue; 37 int a = 0, b = 0, dam = 0; 38 for(int j = n; j < N; j++) 39 { 40 if((1 << j) & i){ 41 b++; 42 dam += x[j]; 43 } 44 } 45 if(dam >= p) 46 continue; 47 for(int j = 0; j < n; j++) 48 { 49 if((1 << j) & i) 50 a++; 51 } 52 if(a - b + 1 <= 0) 53 continue; 54 for(int j = 0; j < N; j++) 55 { 56 if((1 << j) & i) continue; 57 dp[i ^ (1 << j)] += dp[i]; 58 } 59 } 60 LL r1 = 0, r2 = fact[N]; 61 for(int i = 0; i < (1 << N); i++) 62 { 63 if(dp[i] == 0) 64 continue; 65 int a = 0, b = 0, dam = 0; 66 for(int j = n; j < N; j++) 67 { 68 if((1 << j) & i){ 69 b++; 70 dam += x[j]; 71 } 72 } 73 for(int j = 0; j < n; j++) 74 { 75 if((1 << j) & i) 76 a++; 77 } 78 if(dam >= p) 79 r1 += dp[i] * fact[N - a - b]; 80 } 81 LL te = __gcd(r1, r2); 82 printf("%lld/%lld ", r1 / te, r2 / te); 83 } 84 return 0; 85 }