C语言怎样输入一个数求各数位之和呢？用for解决...

#include <stdio.h>
main(void)
{
int n,t,sum=0;
scanf("%d",&n);
for(;;)
{
t=n%10;
n=n/10;
sum=sum+t;
if(n<1)
break;
}
printf("%d",sum);
}

#include <stdio.h>
int main()
{
int i;
scanf("%d", &i);
char c[50];
sprintf(c, "%d", i);
int sum = 0;
for (i = 0; c[i]; i++)
sum += c[i] - '0';
printf("sum is %d\n", sum);
return 0;
}

#include<stdio.h>
#include<conio.h>

main()
{
int i,count=0;

printf("please input a num: ");
i=getch()-48;
for(;(i+'0')!='\r';i=getch()-'0')
{
count+=i;
printf("%d",i);
}

printf("\ncount is: %d",count);
getch();
}