特别说明：这里malloc没有用free回收是因为这边的环境是Xcode，加上free提示已经回收错误，故没有回收内存。
代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* 去除字符串里所有的空格 */
char *DeleteBlank(char *src);

int main ()
{
    char *address;
    int *add, *pos, i;

    if ((address = (char *)malloc(50 * sizeof(char))) == NULL) //防止手残多输入空格
    {
        printf("malloc fail!\n");
        exit(1);
    }
    memset(address, 0, 50);

    if ((add = (int *)malloc(4 * sizeof(int))) == NULL)
    {
        printf("malloc fail!\n");
        exit(2);
    }
    memset(add, 0, 4);

    pos = add;
    printf("Please input binary adress 32 bits (sample : 11111111 11111111 11111111 00000000): \n");
    scanf("%[^\n]",address);

    memcpy(address, DeleteBlank(address), 32);

    address = (char *)realloc(address, 32 * sizeof(char));

    for (i = 0; i < 32; i ++)
    {
        *add = (*add) * 2 + (*address++ - '0');
        if (i > 1 && (i + 1) % 8 == 0)
            add ++;
    }

    printf("IP : %d.%d.%d.%d\n", *(pos), *(pos+1), *(pos+2), *(pos+3));

    return 0;
}

char *DeleteBlank(char *src)
{
    char *p = src;
    int i,j;
    for(i=0;src[i];i++)
    {
        if(src[i]==' ')
        {
            for(j = i; src[j]; j++)
                src[j] = src[j+1];
            i--;
        }
    }
    return p;
}

运行结果：