문자열 함수 구현

#define _CRT_SECURE_NO_WARNINGS
 
#include <stdio.h>
#include<stdlib.h>
size_t strlen(const char *str)
{    //문자열 길이 출력
    int a = 0;
    while (str[a] != '\0') {
        ++a;
    }
    return a;
}
 
int strcmp(const char *str1, const char *str2)
{        //문자가 서로 다른곳 까지의 아스키코드 합을 비교함
    int i;
    for (i = 0; (str1[i] != NULL) || (str2[i] != NULL); i++) {
        if (str1[i] == str2[i])
            continue;
        else if (str1[i] > str2[i]) {
            return 1;
        }
        else if (str1[i] < str2[i]) {
            return -1;
        }
    }
    return 0;
}
 
char * strcpy(char * destination, const char * source)
{    //문자열 복사
    int i;
    for (i = 0; source[i] != NULL; i++) {
        destination[i] = source[i];
    }
    destination[i] = '\0';
    return destination;
}
 
int main()
{
    int result[32];
    int index = 0;
    char arr[32];
 
    result[index++] = strcmp("asdf", "asdfg");
    result[index++] = strcmp("asdf", "asdf");
    result[index++] = strcmp("asdg", "asdf");
    result[index++] = strcmp("asdf", "asdf");
    result[index++] = strcmp("00", "0011");
    result[index++] = strcmp("00", "100");
    result[index++] = strcmp("00", " 00");
    result[index++] = strcmp("0", " 0");
    result[index++] = strcmp("0", "0 ");
    result[index++] = strcmp("0", "0");
    result[index++] = strcmp(" ", " ");
 
    strcpy(arr, "asdf1234!@#$");
    result[index++] = strcmp("asdf1234!@#$", arr);
    strcpy(arr, "");
    result[index++] = strcmp("asdf1234!@#$", arr);
    result[index++] = strcmp("", arr);
 
    result[index++] = strlen("");
    result[index++] = strlen(" ");
    result[index++] = strlen(" \t");
    result[index++] = strlen(" \t\r\n\"");
    result[index++] = strlen("asdf");
    result[index++] = strlen("asdf  ");
    result[index++] = strlen("  asdf");
    result[index++] = strlen("  asdf  ");
    result[index++] = strlen("  asdf  \t");
 
    for (int i = 0; i < index; i++)
    {
        printf("%d : %d\n", i, result[i]);
    }
    system("pause");
    /*
    Expected Result:

    0 : -1
    1 : 0
    2 : 1
    3 : 0
    4 : -1
    5 : -1
    6 : 1
    7 : 1
    8 : -1
    9 : 0
    10 : 0
    11 : 0
    12 : 1
    13 : 0
    14 : 0
    15 : 1
    16 : 2
    17 : 5
    18 : 4
    19 : 6
    20 : 6
    21 : 8
    22 : 9
    */
}