题解 | #素数回文#

#include <string.h>
#include <stdio.h>
#define MAX 20

int is_prime(long int num);

int main(void)
{
    char str[MAX] = {0};
    char ch = 0;
    long int t = 0;
    int i = 0, j = 0;

    while ('\n' != (ch = getchar()))
    {
        *(str + i) = ch;
        i++;
    }
    j = strlen(str) - 2;
    while (j > -1)
    {
        *(str + i) = *(str + j);
        i++;
        j--;
    }
    // 将字符串中的数据转换为格式化数据
    sscanf(str, "%ld", &t);
    printf("%s\n", is_prime(t) ? "prime" : "noprime");
    
    return 0;
}

int is_prime(long int num)
{
	int flag = 1;
	for (long int i = 2; (i * i) <= num; i++)
	{
		if (num % i == 0)
		{
			flag = 0;
			break;
		}
	}
	
	return flag;
}