HDOJ 2161 Primes【素数】

Primes

Time Limit: 1000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 9565    Accepted Submission(s): 4014

Problem Description

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

 

Input

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

 

Output

The output should consists of one line for every number, where each line first lists 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

题目链接： HDOJ 2161 Primes【素数】

题意： 判断一个数是否为素数，本题 1 , 2 都不是素数      条件 n<=0 结束 程序

已AC代码：

#include
#include
int prime[20000];
void into_prime()
{
	memset(prime,0,sizeof(prime));
	for(int i=2;i*i<=16000;++i)
	{
		if(prime[i]==0)
			for(int j=i*i;j<=16000;j+=i)
				prime[j]=1;
	}
	prime[0]=prime[1]=prime[2]=1;//本题 1 , 2 都不是素数 
}
int main()
{
	into_prime();
	int n,CASE=1;
	while(scanf("%d",&n)!=EOF)
	{
		if(n<=0)//条件 n<=0 结束 
			break;
		printf("%d: ",CASE++);
		if(prime[n]==0)
			printf("yes\n");
		else
			printf("no\n");
	}
	return 0;
}