ZOJ 2723 Semi-Prime

Semi-Prime

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Time Limit: 2 Seconds       Memory Limit: 65536 KB

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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.

Input

There are several test cases in the input. Each case contains a single integer 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".

Sample Input

3
4
6
12

Sample Output

No
Yes
Yes
No

好吧 我觉得我英语实在是要提升了！！！我了个去！！！这句话it can be decompounded to TWO prime numbers我把它理解为可以弄成两个素数的和了！！！然后就考虑打表去做，然后一直数据量太大！时间好长，然后我就弄出来这种理解的做法了，输进12，刺眼的YES！！居然样例都过不了。。。我开始审查我的代码了。。。开始想 为啥12过不了。。。不对，按我的想法，12=5+7。。这不俩素数嘛！！！我晕。。。开始仔细看题。。。这个单词实在不知道是啥。。。但是既然不是加。。。那就是乘了！！乘的话就水多了，直接求有多少个质因子，如果只有两个，那就YES。。。。

#include 
using namespace std;

int prim[1000002];
void pri()
{
    prim[0] = prim[1] = 0;
    for (int i = 2; i <= 1000000; i++)
        prim[i] = i;
    for (int i = 2; i < 500000; i++){
        if (prim[i]){
            for (int j = 2; j * i <= 1000000; j++){
                prim[j * i] = 0;
            }
        }
    }
}
int main()
{
    int n, i, q;
    pri();
    while (scanf("%d", &n) != EOF){
        i = 0;
        q = 0;
        while (n != 1){
            if (prim[i]){
                while (n % prim[i] == 0){
                    n = n / prim[i];
                    q++;
                }
            }
            i++;
        }
        if (q == 2)
            printf("Yes\n");
        else
            printf("No\n");
    }
    return 0;
}