判断一个数是否为素数的方法

一、如何写一个判断某输入数字是否为素数（即质数）？

　　简单来说有两种方法：假设从键盘输入一个整数n

【方法一】判断n是否能被2~n-1间的整数除

 1 int isPrime(int k)
 2 {
 3     int j;
 4     for ( j=2; j<k; j++ )    
 5     {
 6         if(k%j==0)    // 如果不为素数返回0 
 7         {
 8              return 0;
 9         }
10         }
11     return 1;    // 反之则返回1 
12 }

【方法二】判断n是否能被2~√n间的整数除

 1 int isPrime(int k)
 2 {
 3     int j;
 4     for ( j=2; j<=sqrt(k); j++ )    
 5     {
 6         if(k%j==0)    // 如果不为素数返回0 
 7     　　{
 8            return 0;
 9         }
10     }
11     return 1;    // 反之则返回1 
12 }

import:方法一与方法二中，后者的空间复杂度更小，效率更高，不易出错，亲测，五星good job (๑•̀ㅂ•́)و✧

·············································································Graceful Line···············································································································

计算机小白懵懂求学

敬请批评指正！谢谢！

----yuhaow