C高级5改写

#include 
char* My_strcpy(char *p1,char *p2)
{
    char *p3 = p1;
    for(;*p2!=0;p1++,p2++)
    {
        *p1 = *p2;
    }
    return p3;
}
int My_strcmp(char *p1,char *p2)
{
    for(;;p1++,p2++)
    {
        if(*p1-*p2 != 0)
        {
            return *p1-*p2;
            break;                                       
        }

        if(*p1 == 0 && *p2 == 0)
        {
            return 0;
            break;
        }
    }
}
char *  My_strcat(char *p1,char *p2)
{
    char *p3 = p1;                                            
    while(p1!=0)
    {
        p1++;
    }
    for(;p2 != 0;p2++,p1++)
    {
        *p1 = *p2;
    }
    *p1 = 0;
    return p3;
}
int main(int argc, const char *argv[])
{
    char c[100] = "";
   char *p = c;
   char b[100] = "";
   char *pb = b;
   int len = 0;                                        
   int i = 0;
   printf("请输入字符串");
   scanf("%s",p);
   printf("请输入字符串");
   scanf("%s",pb);
   for(int i=0; *(p+i) != 0;i++)
   {
       len++;
   }
   printf("my_strlen=%d\n",len);
   printf("-------------------------------\n");
*  My_strcpy(pb,p);
   printf("%s\n",b);
   int num = 0;
   num = My_strcmp(pb,p);
   printf("%d\n",num);*/
   My_strcat(p,pb);
     printf("%s\n",c);
     return 0;
 }