程序代码：

#include <stdio.h>

#define NUL        ('\0')
#define notZero(x) ((x)!=0)

char *
foo (char *s, unsigned n)
{
  int  i,  i2;
  char *p = s;
  char buf[32];

 

  i = 0;
  do
    buf[i++] = '0' + (n%10U);
  while ((n/=10U));

  i2   = i % 3;
  p[0] = buf[i-1];
  p[1] = buf[i-2];
  p[i2]= ',';
  p   += i2 + notZero(i2);
  i   -= i2;

  while (i > 2)
    {
      p[0] = buf[i-1];
      p[1] = buf[i-2];
      p[2] = buf[i-3];
      p[3] = ',';
      p   += 4;
      i   -= 3;
    }

  p[-1] = NUL;
  return s;
}

char *

foos (char *s, int n)
{
  *s = '-';
  return  n < 0  ?  foo(s+1, -n) -1
                 :  foo(s  ,  n);
}


int main (void)
{
  char buf[1024];
  int  i0 = 0;
  int  i1 = 1234567;
  int  i2 = -1234567;

  printf ("%10d : %10s\n", i0, foos(buf,i0));
  printf ("%10d : %10s\n", i1, foos(buf,i1));
  printf ("%10d : %10s\n", i2, foos(buf,i2));
  return 0;
}

程序代码：

#include<stdio.h>
int main()
{
    char number1[1000],number2[1000],ch;
    int i,j,k=1,sign=0;
    printf("请输入任意整数：");
    for(i=0;(ch=getchar())!='\n';)
    {
        if(ch=='-')
        {
            sign=1;//负数标记
        }    
        else
        {
            number1[i]=ch;//把除负号的数字输入数组1
            i++;
        }
    }
    i--;//i为最后一个数字序号
    for(j=1;i>=0;i--,j++,k++)//完成逆置并添加‘,’到数组2，此时为逆序
    {
        number2[j]=number1[i];
        if(k%3==0)
        {
            number2[++j]=',';
        }
    }
    j--;
    if(number2[j]==',')//开始正序输出
    {
        j--;
    }
    if(sign==1)
        putchar('-');
    for(;j>=1;j--)
        printf("%c",number2[j]);
    printf("\n");
    return 0;
}