Question

帮我看看程序吧，从键盘输入任意一个整数n，编程计算并输出1～n之间所有素数之和 ，怎么改啊

#include <stdio.h>
#include <stdlib.h>
int prime(int i,int n );

int main()
{
int sum = 0;
int ret;
int b;
int i = 0;
int n;

printf("Please input a number");
scanf("%d",&n);
ret = prime (i,n);
for (i = 3;i <= n;i++)
{
if (ret == 1)
{
b = i;
}
else
{
b = 0;
}

}
sum = sum + b;

if (ret == 0)
{
b = 0;
}
else
{
b = prime(i,n);
}
sum = sum + b;

printf("The final sum is %d",sum);
printf("program is over");
return 0;
}

int prime(int i,int n)
{
int j;
int a ;
if (n <2)
{
printf("It's not a prime.");
}
if (n == 2)
{
return 2;
}
else
{
for (i = 3;i <= n;i++)
{
for (j = 2;j < n ;j++)
{
a = i % j;

if (a != 0)
{
return i;
}
else
{
return 0;
}
}

}

return i;
}
}

Answer 1

//没有那么复杂，下面是在你的程序基础上修改的。
#include <stdio.h>
#include <stdlib.h>
int prime(int n); //判断素数，是返回1，否则返回0.
int main()
{
int sum = 0;
int ret;
int i = 0;
int n;

printf("Please input a number");
scanf("%d",&n);
for (i = 1;i <= n;i++)
{
ret = prime(i);
if (ret == 1)
{
sum +=i; //求和。
}
}
printf("The final sum is %d",sum);
printf("program is over");
return 0;
}

int prime(int n)
{
int j;
int a;
if (n <2)
{
return 0;
}
if (n == 2)
{
return 1;
}
else
{
for (j = 2;j < n ;j++)
{
a = n % j;
if(a==0)
{
return 0;
}
}

}

return 1;
}

Answer 2

主函数这样

int main(){
int sum = 0;
int i;
int n;

printf("Please input a number:");
scanf("%d", &n);
for (i = 1;i <= n;i++){
if ( IsPrime(i) ){
sum += i;
}
}

printf("The final sum is %d, program is over.", sum);
return 0;
}

子函数，你自己改了