Create Doubly Linked Lists - C Data Structure

C examples for Data Structure:Linked List

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Description

Create Doubly Linked Lists

Demo Code

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>

typedef struct Horse Horse;       // Define Horse as a type name

struct Horse                      // Structure type definition
{
  int age;/* w ww.  j a  v a  2 s. co m*/
  int height;
  char name[20];
  char father[20];
  char mother[20];
  Horse *next;                    // Pointer to next structure
  Horse *previous;                // Pointer to previous structure
};

int main(void)
{
  Horse *first = NULL;            // Pointer to first horse
  Horse *current = NULL;          // Pointer to current horse
  Horse *last = NULL;             // Pointer to previous horse

  char test = '\0';               // Test value for ending input

  for( ; ; )
  {
    printf("another (Y or N)? ");
    scanf(" %c", &test, sizeof(test));
    if(tolower(test) == 'n')
      break;

    // Allocate memory for each new horse structure
    current = (Horse*) malloc(sizeof(Horse));
    if(first == NULL)
    {
      first = current;            // Set pointer to first horse
     current->previous = NULL;
    }
    else
    {
      last->next = current;       // Set next address for previous horse
      current->previous = last;   // Previous address for current horse
    }
    printf("Enter the name of the horse: ");
    scanf("%s", current->name, sizeof(current->name));

    printf("How old is %s? ", current->name);
    scanf("%d", &current->age);

    printf("How high is %s ( in hands )? ", current -> name );
    scanf("%d", &current->height);

    printf("Who is %s's father? ", current->name);
    scanf("%s", current->father,sizeof(current->father));

    printf("Who is %s's mother? ", current->name);
    scanf("%s", current->mother, sizeof(current->mother));

    current->next = NULL;         // In case it's the last...
    last = current;               // ...save its address
  }

  // Now tell them what we know.
  printf("\n");
  while(current != NULL)          // Output horse data in reverse order
  {
    printf("%s is %d years old, %d hands high,",
               current->name, current->age, current->height);
    printf(" and has %s and %s as parents.\n", current->father,
                                            current->mother);
    last = current;               // Save pointer to enable memory to be freed
    current = current->previous;  // current points to previous in list
    free(last);                   // Free memory for the horse we output
    last = NULL;
  }
  first = NULL;
  return 0;
}

Result


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