[求助]帮忙编一道程序题(急)

编写一个函数,判断从健盘输入的整数是否是素数,由主函数调用并输出判断结果?
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这种题好像书上都有答案的
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呵呵..我不会做.可不可以帮我编一下
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#include <stdio.h>
#include <conio.h>
#include <math.h>
int judge(int);
void main(void)
{
int num;
clrscr();
printf("Please input num:\n");
scanf("%d",&num);
if(0==judge(num))
printf("%d is not su shu\n",num);
else
printf("%d is su shu\n",num);
getch();
}
int judge(int num)
{
int i;
for(i=2;i<=sqrt(num);i++)
if(num%2==0)
return 0;
return 1;
}
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#include "stdio.h"
void Prime(int);

int main(void){

unsigned int n;

scanf("%u",&n);

Prime(n);

return 0;

}

void Prime(int n){

int i,k=0;

if(n!=2&&n%2==0)

printf("the number is not prime.");

else{

do{

i=3;

if(n==i||n%i!=0)

k=1;
i+=2;

}while(i*i<=n);

if(k==1)

printf("the number is prime.");

else

printf("the number is not prime.");

}

return ;

}

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[QUOTE]#include <stdio.h>
#include <conio.h>
#include <math.h>
int judge(int);
void main(void)
{
int num;
clrscr();
printf("Please input num:\n");
scanf("%d",&num);
if(0==judge(num))
printf("%d is not su shu\n",num);
else
printf("%d is su shu\n",num);
getch();
}
int judge(int num)
{
int i;
for(i=2;i<=sqrt(num);i++)
if(num%2==0)
return 0;
return 1;
}[/QUOTE]

个人感觉效率不是很好.
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#include "stdio.h"
void Prime(int);

int main(void){

unsigned int n;

scanf("%u",&n);

Prime(n);

return 0;

}

void Prime(int n){

int i,k=0;

if(n!=2&&n%2==0)

printf("the number is not prime.");

else{

do{

i=3;

if(n==i||n%i!=0){

k=1;
i+=2;
}
else{

k=0;

break; //刚才漏掉了
}

}while(i*i<=n);

if(k==1)

printf("the number is prime.");

else

printf("the number is not prime.");

}

return ;

}

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我想请您试一下,有没有得到正确答案?

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...
那楼上的人为num%2==0处理好捏?
我也想知道捏。。。

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哦 错了,
应该是
if(num%i==0)
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