Prime Number Definition
An integer greater than one is called a prime number if its only positive divisors (factors) are one and itself. For instance, 2, 11, 67, 89 are prime numbers but 8, 20, 27 are not.
Semi-Prime Number Definition
An integer greater than one is called a semi-prime number if it can be decompounded to TWO prime numbers. For example, 6 is a semi-prime number but 12 is not.
Your task is just to determinate whether a given number is a semi-prime number.
素数定义
如果一个大于1的整数只有一个正整数（因子）是一个整数，那么它就称为素数。 例如，2,11,67,89是素数，但8,20,27不是。
半素数定义
如果一个大于1的整数可以分解为两个素数，则称其为一个半素数。 例如，6是一个半素数，但12不是。
你的任务只是确定一个给定的数字是否是一个半素数。
Input
There are several test cases in the input. Each case contains a single integer N (2 <= N <= 1,000,000)
输入中有几个测试用例。 每个案例包含一个整数N（2 <= N <= 1,000,000）
Output
One line with a single integer for each case. If the number is a semi-prime number, then output "Yes", otherwise "No".
一行每个案件都有一个整数。 如果数字是半素数，则输出“是”，否则输出“否”。
Sample Input
3
4
6
12
Sample OutputNo
Yes
Yes
No
what i have learned:
set search
1 #include<iostream> 2 #include<vector> 3 #include<set> 4 #include<cmath> 5 using namespace std; 6 7 vector<int> v; 8 set<int> s; 9 10 void pt(int a, int b) 11 { 12 for(int i = a; i <= b; i++) 13 { 14 if(i != 2 && i % 2 == 0) 15 continue; 16 for(int j = 3; j * j <= i; j += 2) 17 { 18 if(i % j == 0) 19 goto RL; 20 } 21 v.push_back(i); 22 RL: continue; 23 } 24 } 25 26 int main() 27 { 28 pt(2, 500000); 29 int i, j, p; 30 for(int i = 0; i < v.size(); i++) 31 { 32 for(int j = 0; j < v.size(); j++) 33 { 34 p = v[i] * v[j]; 35 if(p < 1000000) 36 s.insert(p); 37 else 38 break; 39 } 40 } 41 42 int n; 43 set<int>::iterator it; 44 while(cin >> n) 45 { 46 it = s.find(n); 47 if(it != s.end()) 48 cout << "Yes" << endl; 49 else 50 cout << "No" << endl; 51 } 52 return 0; 53 }
