CK_C++_Chapter9

#include <stdio.h>
#include <string.h>
#pragma warning (disable:4996)

struct login_info
{
    char id[20];
    char passwd[20];
};

typedef struct login_info LOGIN_INFO;

LOGIN_INFO arr[100];
int num = 0;

int main(void)
{
    char id[20], passwd[20];
    int i;
    int found;

    while (1)
    {
        printf("ID: ");
        gets(id);

        if (strcmp(id, ".") == 0)
            break;

        found = -1;
        for (i = 0; i < num; i++)
        {
            if (strcmp(id, arr[i].id) == 0)
            {
                found = i;
                break;
            }
        }
        if (found == -1)
        {
            char yesno;
            printf("등록 되지 않은 ID입니다. 회원가입을 하시겠습니까? (Y/N) : ");
            scanf("%c", &yesno);
            fflush(stdin);

            if (yesno == 'y' || yesno == 'Y')
            {
                printf("ID를 입력하세요 : ");
                gets(arr[num].id);
                printf("패스워드를 입력하세요 : ");
                gets(arr[num].passwd);
                num++;
            }
            else
                continue;
        }
        else
        {
            printf("PASSWORD : ");
            gets(passwd);

            if (strcmp(passwd, arr[found].passwd) == 0)
                printf("로그인 되었습니다.\n");
            else
                printf("패스워드가 틀립니다.\n");
        }
    }

    return 0;
}