模拟实现strcat

#include<stdio.h>
char* mystrcat(char* str, const char* dst)
{
    char* ret = str;
    if (str == NULL || dst == NULL)
    {
        return NULL;
    }
    while (*str != '\0')
    {
        str++;
    }
    while (*str++ = *dst++);
    return ret;
}
int main()
{
    char str[20] = "abcdefg";
    char* dst = "higklmn";
    char* ret = mystrcat(str, dst);
    printf("%s\n", ret);
    system("pause");
    return 0;
}