list.c

linux下的Ｃ语言开发

/********************************************************
 * Define, use and print out an ordered linked list 	*
 *							*
 * Usage:						*
 *	list						*
 *							*
 * Note: Demonstration of an ordered linked list	*
 ********************************************************/
#include <stdio.h>
#include <stdlib.h>

/********************************************************
 * Item for our linked list				*
 ********************************************************/
struct item {
    int value;			/* Value of the item */
    struct item *next_ptr;	/* Pointer to the next item */
};

/********************************************************
 * enter -- enter a value in the linked list.		*
 *							*
 * Parameters						*
 *	first_ptr -- pointer th the head of the list	*
 *	value -- value to add to the list		*
 *							*
 * Restrictions: The first entry must be the lowest.	*
 *	The list must have one item already		*
 ********************************************************/
void enter(struct item *first_ptr, const int value)
{
    struct item *before_ptr;		/* Item before this one */
    struct item *after_ptr;		/* Item after this one */
    struct item *new_item_ptr;		/* Item to add */

    /* Create new item to add to the list */

    before_ptr = first_ptr;		/* Start at the beginning */
    after_ptr =  before_ptr->next_ptr;	

    while (1) {
	if (after_ptr == NULL)
	    break;

	if (after_ptr->value >= value)
	    break;

	/* Advance the pointers */
	after_ptr = after_ptr->next_ptr;
	before_ptr = before_ptr->next_ptr;
    }

    new_item_ptr = malloc(sizeof(struct item));
    new_item_ptr->value = value;	/* Set value of item */

    before_ptr->next_ptr = new_item_ptr;
    new_item_ptr->next_ptr = after_ptr;
}
/********************************************************
 * print -- print the linked list			*
 *							*
 * Parameter						*
 *	first_ptr -- pointer to the first item on the 	*
 *			list 				*
 ********************************************************/
void print(struct item *first_ptr)
{
    struct item *cur_ptr;	/* Pointer to the current item */

    for (cur_ptr = first_ptr; cur_ptr != NULL; cur_ptr = cur_ptr->next_ptr) 
	printf("%d ", cur_ptr->value);
    printf("\n");
}

int main()
{
    /* The linked list */
    struct item *head_ptr = NULL;

    head_ptr = malloc(sizeof(struct item));

    head_ptr->value = 0;
    head_ptr->next_ptr = NULL;

    enter(head_ptr, 5);
    enter(head_ptr, 4);
    enter(head_ptr, 8);
    enter(head_ptr, 9);
    enter(head_ptr, 1);
    enter(head_ptr, 2);

    print(head_ptr);
    return (0);
}