ACM HDU Primes(素数判断)

Problem Description

Writea program to read in a list of integers and determine whether or not eachnumber is prime. A number, n, is prime if its only divisors are 1 and n. Forthis problem, the numbers 1 and 2 are not considered primes. 

 

 

Input

Eachinput line contains a single integer. The list of integers is terminated with anumber<= 0. You may assume that the input contains at most 250 numbers andeach number is less than or equal to 16000.

 

 

Output

Theoutput should consists of one line for every number, where each line firstlists the problem number, followed by a colon and space, followed by"yes" or "no". 

 

 

Sample Input

1

2

3

4

5

17

0

 

 

Sample Output

1: no

2: no

3: yes

4: no

5: yes

6: yes

 

/************************************************************************

简单数论，判断素数，，，

**************************************************/

#include<stdio.h>
bool prime(int n)
{
	if(n<=2)
		return false;//  这题好奇葩, 1,2不算素数
	for(int i = 2;i*i<=n;i++)
		if(n%i==0)
			return false;
	return true;
}
int main()
{
	int n,count = 0;//  注意输出时前面的数字是计数的，而不是输入的数字
	while(scanf("%d",&n)&&n>0)
	{
		count++;
		if(prime(n))
			printf("%d: yes
",count);
		else
			printf("%d: no
",count);
	}
	return 0;
}

//  虽然很简单，但是想记下来，慢慢积累。。