1.strcpy:将字符串src拷贝到des里
<1>.void mystrcpy1(char *des,const char* src)//拷贝
{
assert(des != NULL && src != NULL);
while(*src != '\0')
{
*des++ = *src++;
}
*des = '\0';
}
<2>char* mystrcpy2(char *des,const char *src)
{
while(*des++ = *src++);
return des;
}
2.strcmp：比较字符串str1和str2
int mystrcmp(const char *str1,const char *str2)//比较(返回0相等，正数str1大，负数str2大)
{
assert(str1 != NULL && str2 != NULL);
int tmp;
while((tmp = *str1 - *str2) == 0 && *str1 != '\0')//等待str1结束，则已经判断出大小
{
str1++;
str2++;
}
return tmp;
}
3.strcat:将字符串src连接到字符串des后
char* mystrcat(char *des,const char *src)//连接
{
assert(des != NULL && src != NULL);
//注意不能return des，因为des已经走到了'\0'，所以提前让p走到des的首地址
char *p = des;
while(*des != '\0')
{
des++;
}
while(*des++ = *src++);
return p;
}