双向循环链表

/* * Copyright 2014 YU Heng-yang. All rights reserved. *   * cdlist.c - Circular doubly-linked list. * * Modify data to any other types as you like, note also the *  prototypes of interface functions and data compare function. * * 2014-7-6 YU Heng-yang. */#include <stdio.h>#include <stdlib.h>#include <assert.h>#define ALLOC(size) malloc(size)#define FREE(p)     free(p)typedef struct DList *DList;struct DList {int data;DList prev, next;};DList dlist_new(void);DList dlist_insert(DList  dlist, int data);DList dlist_delete(DList  dlist, int data);DList dlist_find(DList  dlist, int data);DList dlist_destroy(DList  dlist);void dlist_traversal(DList  dlist, void (*apply) (DList  dlist, void *arg),     void *arg);void print(DList  dlist, void *arg){assert(arg);printf((char *)arg, dlist->data);}int main(int argc, char *argv[]){#define N 5int i, n;DList dlist = dlist_new();for (i = 0; i < N; i++) {scanf("%d", &n);dlist = dlist_insert(dlist, n);assert(dlist);printf("After insert %d: ", n);dlist_traversal(dlist, print, "%d ");putchar('\n');}for (i = 0; i < N; i++) {scanf("%d", &n);assert(dlist);dlist = dlist_delete(dlist, n);printf("After delete %d: ", n);dlist_traversal(dlist, print, "%d ");putchar('\n');}dlist = dlist_destroy(dlist);assert(dlist == NULL);dlist_traversal(dlist, print, "");assert(dlist == dlist_destroy(dlist));return 0;}DList dlist_new(void){return NULL;}DList dlist_insert(DList  dlist, int data){DList dl = ALLOC(sizeof(*dl));assert(dl);dl->data = data;if (NULL == dlist)dl->prev = dl->next = dl;else {/* head insert */dl->next = dlist;dlist->prev->next = dl;dl->prev = dlist->prev;dlist->prev = dl;}return dlist = dl;}DList dlist_delete(DList  dlist, int data){DList p = dlist_find(dlist, data);if (p) {if (p->next == p) {/* the last element? */FREE(p);dlist = NULL;} else {if (p == dlist)/* head element? */dlist = dlist->next;p->prev->next = p->next;p->next->prev = p->prev;FREE(p);}}return dlist;}DList dlist_find(DList  dlist, int data){DList p;for (p = dlist; p; p = p->next)if (p->data == data || p->next == dlist)break;return p->data == data ? p : NULL;}DList dlist_destroy(DList  dlist){DList p, q;for (p = dlist; p; p = q) {q = p->next;FREE(p);if (q == dlist)break;}return NULL;}void dlist_traversal(DList  dlist, void (*apply) (DList  dlist, void *arg),     void *arg){DList p;assert(apply);for (p = dlist; p; p = p->next) {apply(p, arg);if (p->next == dlist)break;}}