[C로 배우는 알고리즘] Namecard

#include <stdio.h>
//nclude <alloc.h>
#include <stdlib.h>
#include <string.h>

#define NAME_SIZE 21
#define CORP_SIZE 31
#define TEL_SIZE 16
#define REC_SIZE (NAME_SIZE + CORP_SIZE + TEL_SIZE)

typedef struct _card
{
    char name[NAME_SIZE];
    char corp[CORP_SIZE];
    char tel[TEL_SIZE];
    struct _card *next;
} card;

card *head, *tail;

void init_card(void)
{
    head = (card*)malloc(sizeof(card));
    tail = (card*)malloc(sizeof(card));
    tail->next = tail;
    tail->next = tail;
}

void input_card(void)
{
    card *t;
    t = (card*)malloc(sizeof(card));

    printf("\nInput namecard menu : ");
    printf("\n Input name -> ");
        gets(t->name);
    printf("\n Input corporation : ");
        gets(t->corp);
    printf("\n Input telephone : ");
        gets(t->tel);

    t->next = head->next;
    head->next = t;
}

void print_card(card* t, FILE* f)
{
    fprintf(f, "\n%-20s %-30s %-15s",t->name, t->corp, t->tel);
}

void print_header(FILE* f)
{
    fprintf(f,    "\nName            "
                "Corporation    "
                "Telephone number");
    fprintf(f, "\n ----------------------------    "
                " --------------------------------    "
                "----------------");
}

void load_cards(char *s)
{
    FILE *fp;
    card *t;
    card *u;

    if((fp = fopen(s, "rb")) == NULL)
    {
        printf("\n    Error : %s is not exist. ", s);
        return;
    }
    t = head->next;

    while(t != tail)
    {
        u = t;
        t = t->next;
        free(u);
    }
    head->next = tail;

    while(1)
    {
        t = (card*)malloc(sizeof(card));
        if(!fread(t, REC_SIZE, 1, fp))
        {
            free(t);
            break;
        }
        t->next = head->next;
        head->next = t;
    }

    fclose(fp);
}

void save_cards(char* s)
{
    FILE* fp;
    card* t;

    if((fp = fopen(s, "wb")) == NULL)
    {
        printf("\n Error : Disk write failure. ");
        return;
    }
    t = head->next;
    
    while(t!=tail)
    {
        fwrite(t, REC_SIZE, 1, fp);
        t = t->next;
    }

    fclose(fp);
}

int delete_card(char* s)
{
    card* t;
    card* p;
    p = head;
    t = p->next;
    
    while(strcmp(s, t->name) != 0 && t != tail)
    {
        p = p->next;
        t = p->next;
    }

    if(t == tail)
        return 0;

    p->next = t->next;
    free(t);

    return 1;
}

card* search_card(char* s)
{
    card* t;
    t = head->next;

    while(strcmp(s, t->name) != 0 && t != tail)
        t = t->next;

    if(t == tail)
        return NULL;
    else
        return t;
}

int select_menu(void)
{
    int i;
    char s[10];

    printf("\n\nNAMECARD Manager");
    printf("\n-------------------------------------------------");
    printf("\n1. Input Namecard");
    printf("\n2. Delete Namecard");
    printf("\n3. Search Namecard");
    printf("\n4. Load Namecard");
    printf("\n5. Save Namecard");
    printf("\n6. List Namecard");
    printf("\n7. Print Namecard");
    printf("\n8. End Namecard");

    do
    {
        printf("\n\n : select operation -> ");
        i = atoi(gets(s));
    }
    while(i < 0 || i > 8);

    return i;
}

void main(void)
{
    char *fname = "NAMECARD.DAT";
    char name[NAME_SIZE];
    int i;
    card *t;
    init_card();

    while((i = select_menu()) != 8)
    {
        switch(i)
        {
        case 1: input_card();
            break;
        case 2: printf("\n Input name to delete -> ");
            gets(name);
            if(!delete_card(name))
                printf("\n Can't find that name.");
            break;
        case 3: printf("\n Input name to search -> ");
            gets(name);
            t = search_card(name);
            if(t == NULL)
            {
                printf("\n Can't find that name.");
                break;
            }
            print_header(stdout);
            print_card(t, stdout);
            break;
        case 4: load_cards(fname);
            break;
        case 5: save_cards(fname);
            break;
        case 6: t = head->next;
            print_header(stdout);
            while(t != tail)
            {
                print_card(t, stdout);
                t = t->next;
            }
            break;
        case 7: t = head->next;
            print_header(stdout);
            while(t != tail)
            {
                print_card(t, stdout);
                t = t->next;
            }
            break;
        }
    }

    printf("\n\nProgram ends...");
}