Ubuntu-gr Forum

#include <stdio.h>   // printf(), puts(), scanf(), fgets(), getchar(), putchar()
#include <stdlib.h>  // malloc(), free(), strtol(), exit(), EXIT_SUCCESS, EXIT_FAILURE
#include <stdbool.h> // bool, true, false
#include <ctype.h>   // isspace()
#include <string.h>  // strcmp()

#define MAX_INPUT     (255+1)
#define LEN_WORD      (50+1)

typedef struct node {
    char animal[LEN_WORD];
    struct node *next;
} Node;

typedef struct {
	Node *head;
	int len;
} List;


/*******************************************************************
 * read_line: Skips leading white-space characters, then reads the *
 *            remainder of the input line and stores it in str.    *
 *            Truncates the line if its length exceeds n.          * 
 *            Returns the number of characters stored.             *
 *******************************************************************/ 
int read_line(char str[], int n)
{
    int ch, i = 0;

    while (isspace(ch = getchar()))
        ;
    while (ch != '\n' && ch != EOF) {
        if (i < n)
            str[i++] = ch;
        ch = getchar();
    }
    str[i] = '\0';
    return i;
}

/*********************************************************************
 * valid_input: Skips leading white-space characters, then reads the *
 *            first character and stores it in tmp. Returns whether  *
 *            tmp is a valid input (char between '1' and '4').       * 
 *********************************************************************/ 
bool valid_input(char *s)
{
    char tmp, *ch = s;
    
    for (; *ch && isspace(*ch); ch++)
        ; // skip any blanks
    tmp = *ch;
    
    if (tmp < '1' || tmp > '4')
        return false;

    if (*++ch)
        for (; *ch; ch++)
            if (!isspace(*ch))
                return false;

    return true;
}


/*********************************************************************
 * insert:  Add a new node to a sorted list. List is sorted          *
 *          alphabetically. Asks user for an animal name and checks  *
 *          if it is already exists in the list.                     *
 *          Returns true if node stored properly, else false.        *
 *********************************************************************/ 
bool insert(Node **list)
{
    Node *cur, *prev, *new_node;

    new_node = malloc(sizeof(Node));
    if (new_node == NULL) {
        puts("The zoo is full; can't add more animals.");
        return false;
    }
        
    printf("\nEnter animal: ");
    read_line(new_node->animal, LEN_WORD);

    for (cur = *list, prev = NULL;
         cur != NULL && strcmp(new_node->animal, cur->animal) > 0;
         prev = cur, cur = cur->next)
        ;
         
    if (cur != NULL && (!strcmp(new_node->animal, cur->animal))) {
        printf("%s already in the zoo.\n", new_node->animal);
        free(new_node);
        return false;
    }
    
    new_node->next = cur;
    if (prev == NULL)
        *list = new_node;
    else
        prev->next = new_node;    
    
    printf("%s was added.\n", new_node->animal); 
    return true;    
}

/*********************************************************************
 * delete:  Delete a node from a sorted list. List is sorted         *
 *          alphabetically. Asks user for an animal name and checks  *
 *          if it is already exists in the list.                     *
 *          Returns true if node removed properly, else false.       *
 *********************************************************************/ 
bool delete(Node **list)
{
    Node *cur, *prev;
    char animal[LEN_WORD];
    
    printf("\nEnter the name of the animal that you want to kill: ");
    read_line(animal, LEN_WORD);
    
    for (cur = *list, prev = NULL;
         cur != NULL && strcmp(animal, cur->animal) > 0;
         prev = cur, cur = cur->next)
        ;
    
    if (cur == NULL || strcmp(animal, cur->animal)) {
        puts("No animal with such a name. Fortunately!");
        return false;
    }
    
    if (prev == NULL)
        *list = cur->next;    
    else
        prev->next = cur->next;
    
    printf("You just killed the %s. Are you completely heartless?\n", cur->animal);
    free(cur);
    return true;
}

/********************************************************
 * list_print:  Prints the contents of a linked list.   * 
 ********************************************************/ 
void list_print(Node *list)
{
    puts("\nAnimals sorted by name: ");
    for (; list != NULL; list = list->next)
        printf("%s, ", list->animal);
    putchar('\n');
    putchar('\n');
}

/*********************************************************************
 * list_destroy:  Deallocate memory of all members of a linked list. * 
 *********************************************************************/ 
void list_destroy(Node *list)
{
    if (list == NULL)
        return;

    Node *dummy = NULL;
    for (; list != NULL; list = dummy) {
        dummy = list->next;
        free(list);
    }
}


/**************************************************************************
 * main:  Prints a list of available choices and asks user to select one. *
 *        User can insert or kill an animal, print a sorted list of all   *
 *        animals or quit the program.
 *************************************************************************/ 
int main(void)
{
    char input[MAX_INPUT];
    List zoo;
    
    zoo.head = NULL;
    zoo.len = 0;

    puts("Welcome to the zoo!");
    puts("-------------------");
    for (;;) {
        puts("\n1. Insert animal\n2. Kill animal\n"
             "3. Print all animals\n4. Quit\n");
        
        if (valid_input(fgets(input, sizeof(input), stdin)))
            switch(strtol(input, NULL, 10)) {
                case 1: 
                    if (insert(&zoo.head))
                        zoo.len++;
                    break;
                case 2: 
                    if (delete(&zoo.head))
                        zoo.len--;
                    break;
                case 3: 
                    list_print(zoo.head);
                    printf("There are %d animals in total.\n", zoo.len);
                    break;
                case 4: 
                    puts("\nGoodbye!"); 
                    goto exit_success;
                    break;
            }
        else
            puts("invalid option");
    }
    
exit_success:   
    list_destroy(zoo.head);
    exit(EXIT_SUCCESS);
}