数据结构之双链表

一.代码

1.1.前言：

1.双链表与单链表有许多相似之处，区别在于插入与删除。所以只选取不同点的代码。

2.为了简化操作，将头节点的数据部分存储链表的长度，此时，就不必遍历链表了。

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

#define false 0
#define true 1

typedef struct node {
	int data;
	struct node* next;
	struct node* prior;
}DLinkList;

DLinkList* init(DLinkList* List) {
	List = (DLinkList*)malloc(sizeof(DLinkList));
	if (List) {
		List->data = 0;//元素数量
		List->next = NULL;
		List->prior = NULL;
		return List;
	}
	printf("fail to allocate menory\n");
	return List;
}

int listInsert(DLinkList* List, int pos, int value) {
	if (pos < 1) {
		printf("abnormal position\n");
		return false;
	}
	if (List) {
		DLinkList* temp = List;
		int position = 0;
		while (temp->next != NULL && position < pos - 1) {
			position++;
			temp = temp->next;
		}
		if (position == pos - 1) {
			DLinkList* new_node = (DLinkList*)malloc(sizeof(DLinkList));
			if (new_node) {
				new_node->data = value;
				if (temp->next != NULL)
					temp->next->prior = new_node;
				new_node->next = temp->next;
				temp->next = new_node;
				new_node->prior = temp;
				List->data++;
				return true;
			}
			printf("fail to allocate menory\n");
			return false;
		}
		printf("abnormal position\n");
		return false;
	}
	printf("the list doesn't exist\n");
	return false;
}

void print(DLinkList* List) {
	if (List) {
		DLinkList* temp = List;
		printf("ascending order：");
		while (temp->next!=NULL) {
			printf("%d ", temp->next->data);
			temp = temp->next;
		}
		printf("\n");
		printf("descending order：");
		while (temp->prior != NULL) {
			printf("%d ", temp->data);
			temp = temp->prior;
		}
		printf("\n");
		return;
	}
	printf("the list doesn't exist\n");
}

int listDelete(DLinkList* List,int pos,int* value) {
	if (pos < 1) {
		printf("abnormal position\n");
		return false;
	}
	if (List) {
		DLinkList* temp = List;
		int position = 0;
		while (temp->next != NULL && position < pos - 1) {
			position++;
			temp = temp->next;
		}
		if (temp->next != NULL && pos - 1 == position) {
			*value = temp->next->data;
                        DLinkList* deletde_node=temp->next;
			if (temp->next->next != NULL)
				temp->next->next->prior = temp;
			temp->next = temp->next->next;
			List->data--;
                        free(deletde_node);
			return true;
		}
		printf("abnormal position\n");
		return false;
	}
	printf("the list dosen't exist\n");
	return false;
}

int length(DLinkList* List) {
	return List->data;
}

int main() {
	DLinkList* List = NULL;
	List = init(List);
	if (List) {
		int value;
		listInsert(List, 1, 1);
		listInsert(List, 1, 2);
		listInsert(List, 1, 3);
		listInsert(List, 1, 4);
		listInsert(List, 1, 5);
		printf("the length of List：%d\n",length(List));
		print(List);
		if (listDelete(List, 5, &value))
			printf("deleted data：%d\n", value);
		printf("the length of List：%d\n", length(List));
		print(List);
	}
	return 0;
}

二.运行结果

三.遇到的问题

3.1.插入元素时需要考虑下一个元素是否存在，因为需要改变该元素的前驱指针

3.2.删除元素时同理。