C language notes: base conversion with 32-bit binary decimal IP address translation problem

Original link: http://c.biancheng.net/c/

Problem description:
Suppose you want to write a program, a 32-bit binary IP address (32 characters long and 1 0) is converted to decimal point format and output. Point IP address by decimal notation 32 from low to high (right to left) a packet eight, four times in total, any 8-bit binary number corresponding to the decimal part of the IP address is valid.

C language code for:

/*
问题描述：
假设正在读取表示IP地址的字节流，任务是将32个字符长的1和0（位）序列转换为点分十进制格式，IP地址的点分十进制
格式是通过将32位字节流一次分组8位，并将二进制表示转换为十进制表示形式 
*/
#include <stdio.h>
#include <string.h>
#define base 2
int main(void)
{
 int n;
 printf("请输入需要将32位二进制IP地址转化为点分十进制格式的数量：");
 scanf("%d",&n);
 for(int i=0;i<n;i++)
 {
  char s[40];
  int sum=0,flag=0;//flag为控制分隔符"."的输出 
  scanf("%s",s);
  for(int j=0;j<strlen(s);j++)
  {
   sum=sum*base+s[j]-'0';//此处是重点，每8位二进制数转换为十进制数
   if(j%8==7)//当j=7,15,23,31时开始输出 
   {
    if(flag)
    {
     printf(".");//输出第一个八位二进制对应的十进制数时，不输出"."
    }
    printf("%d",sum);
    sum=0;//sum置零，运算第二个八位二进制对应的十进制数 
    flag=1;//从第二个开始输出"." 
   }
  }
  printf("\n");
 }
 return 0;
}

Output: