Question

用C语言编程:用函数求1~n之和,要求函数原型为long fnsun(int n)

Answer 1

#include<stdio.h>
long fnsun(int n)
{
long s=0;
int i;
for(i=1;i<=n;i++)
s+=i;
return s;
}
void main()
{
int n;
scanf("%ld",&n);
printf("sum=%ld\n",fnsun(n));
}

Answer 2

#include<stdio.h>
long fusun(int);
main()
{
int n;
long sum;
printf("input a number:");
scanf("%d",&n);
sum=fusun(n);
printf("sum=%d\n",sum);
}
long fusun(int n)
{
int m=n;
if(n>0)
return fusun(--m)+n;
else
return 0;
}

Answer 3

long int fnsum(int n)
{
int sum = 0;
for(int i =0;i<=n;i++)
{
sum = sum+i;
}
return sum;
}