题意:https://nanti.jisuanke.com/t/17320
The frequent subset problem is defined as follows. Suppose U={1, 2,…\ldots…,N} is the universe, and S1S_{1}S1, S2S_{2}S2,…\ldots…,SMS_{M}SM are MMM sets over UUU. Given a positive constant α\alphaα, 0<α≤10<\alpha \leq 10<α≤1, a subset BBB (B≠0B \neq 0B≠0) is α-frequent if it is contained in at least αM\alpha MαM sets of S1S_{1}S1, S2S_{2}S2,…\ldots…,SMS_{M}SM, i.e. ∣{i:B⊆Si}∣≥αM\left | \left \{ i:B\subseteq S_{i} \right \} \right | \geq \alpha M∣{i:B⊆Si}∣≥αM. The frequent subset problem is to find all the subsets that are α-frequent. For example, let U={1,2,3,4,5}U=\{1, 2,3,4,5\}U={1,2,3,4,5}, M=3M=3M=3, α=0.5\alpha =0.5α=0.5, and S1={1,5}S_{1}=\{1, 5\}S1={1,5}, S2={1,2,5}S_{2}=\{1,2,5\}S2={1,2,5}, S3={1,3,4}S_{3}=\{1,3,4\}S3={1,3,4}. Then there are 333 α-frequent subsets of UUU, which are {1}\{1\}{1},{5}\{5\}{5} and {1,5}\{1,5\}{1,5}.
Input Format
The first line contains two numbers N and α\alpha α, where N is a positive integers, and α\alpha α is a floating-point number between 0 and 1. Each of the subsequent lines contains a set which consists of a sequence of positive integers separated by blanks, i.e., line i+1 contains SiS_{i}Si, 1≤i≤M1 \le i \le M1≤i≤M . Your program should be able to handle NNN up to 202020 and MMM up to 505050.
Output Format
The number of α\alphaα-frequent subsets.
样例输入
15 0.4 1 8 14 4 13 2 3 7 11 6 10 8 4 2 9 3 12 7 15 2 8 3 2 4 5
样例输出
11
#include<cstdio> #include<cstring> #include<algorithm> #include<iostream> #include<queue> #include<map> #include<math.h> #include<string> #include<vector> using namespace std; #define INF 0x3f3f3f3f #define LL long long #define N 500 int a[N]; int main() { int n,ans=0,x; double m; char r; scanf("%d%lf",&n,&m); while(scanf("%d%c",&x,&r)!=EOF) { a[ans]+=1<<(x-1); if(r=='\n') ans++; } int w=ceil(m*ans); int sum=0; for(int i=1;i<(1<<n);i++) { int t=0; for(int j=0;j<ans;j++) { if((i & a[j]) ==i) t++;///优先级 要带括号 } if(t>=w) sum++; } printf("%d\n",sum); return 0; }