strlen/strcpy/strcat的模拟实现

char* my_strcat(char* dest, const char* src)
{
assert(dest != NULL);//字符串要以‘\0’结束，目标空间要足够大，且可修改
assert(src != NULL);
char* ret = dest;
//1，找到目的字符串的\0;
while (*dest != '\0')
{
dest++;
}
//2，追加
while (*dest++ = *src++)
{
;
}
return ret;
}
int main()
{
char arr1[30] = "hello";//目的空间足够大，要以“\0”结束,可修改
char arr2[] = "world";
//strcat(arr1, arr2);
my_strcat(arr1, arr2);
printf("%s\n", arr1);
return 0;
}

char* my_strcpy(char* dest, const char* src)
{
assert(dest != NULL);//字符串要以‘\0’结束，目标空间要足够大，且可修改
assert(src != NULL);
char* ret = dest;
//拷贝src指向的字符串到dest指向的空间，包含\0,返回目的空间的起始位置
//while (*src != '\0')
//{
// *dest = *src;
// dest++;
// src++;
//}
//*dest = *src;//"\0"
while (*dest++ = *src++)//精简写法
{
;
}
return ret;
}
int main()
{
char arr1[] = "abcdefghi";
char arr2[] = "bit";
strcpy(arr1, arr2);
my_strcpy(arr1, arr2);
printf("%s\n", arr1);
return 0;
}

int my_strlen(const char* str)
{
/*int count = 0;
assert(str != NULL);
while (*str != '\0')
{
count++;
str++;
}
return count;*/
//递归写法
if(*str !='\0')
return my_strlen(str + 1) + 1;

}
int main()
{
int len = strlen("abcdfe");
printf("%d\n", len);
int len1 = my_strlen("abcdef");
printf("%d\n", len1);
if (strlen("abc") - strlen("abcdef") > 0)
printf("hehe");
//size_t == unsigned int
return 0;
}