程序代码：

方式一：
// 把字符串str中的子字符串substr1用子字符串substr2替换
char* SwapSubstr(char *dest, char *source, char*substr1, char*substr2)
{
    char *pstr = source;
    char *pstr1 = dest;
    unsigned int i;
  
    for (i=0;i<strlen(source)-strlen(substr1)+1;i++)
    {
        if (0==strncmp(pstr,substr1,strlen(substr1)))
        {
            strcat(pstr1,substr2);
            pstr += strlen(substr1);
            pstr1 += strlen(substr2);
        }
        else
            *pstr1++ = *pstr++;
    }
    *pstr1 = 0;
    return dest;
}