双向链表——C++描述

#include "pch.h"
#include <iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>

//双向链表的节点的构建
struct Node {
	int key;
	Node *next, *pre;//前向节点指针和后向节点指针
};

Node *nil;//头节点

Node* listsearch(int key) {
	//寻找值为key的节点
	Node *cur = nil->next;
	while (cur != nil && cur->key != key) {
		cur = cur->next;
	}
	return cur;//返回该结点的地址
}

void init() {//生成结点
	nil = (Node *)malloc(sizeof(Node));
	nil->next = nil;
	nil->pre = nil;
}

void printList() {
	//打印结点
	Node *cur = nil->next;
	int isf = 0;
	while (1) {
		if (cur == nil) {
			break;
		}
		if (isf++ > 0) {
			printf(" ");
		}
		printf("%d", cur->key);
		cur = cur->next;
	}
	printf("\n");
}

void deleteNode(Node *t) {//删除结点
	if (t == nil) {
		return;
	}
	t->pre->next = t->next;
	t->next->pre = t->pre;
	free(t);
}

//删除下一个
void deleteFirst() {
	deleteNode(nil->next);
}

//删除前一个
void deleteLast() {
	deleteNode(nil->pre);
}
//删除搜索到的结点
void deleteKey(int key) {
	deleteNode(listsearch(key));
}

//插入结点
void insert(int key) {
	Node *x = (Node *)malloc(sizeof(Node));
	x->key = key;
	//在头节点后添加元素
	x->next = nil->next;
	nil->next->pre = x;
	x->pre = nil;
}

int main()
{
	int key, i,n;
	int size = 0;
	char com[20];
	int np = 0, nd = 0;
	scanf_s("%d", &n);
	init();//初始化，生成头结点
	for (i = 0; i < n; i++) {
		scanf_s("%s%d", com, &key);
		if (com[0] == 'i') {
			insert(key);
			np++;
			size++;
		}
		else if (com[0] == 'd') {
			if (strlen(com) > 6) {
				if (com[6] == 'F') {
					deleteFirst();
				}
				else if (com[6] == 'L') {
					deleteLast();
				}	
			}
			else {
				deleteKey(key);
				nd++;
			}
			size--;
		}	
	}
	printList();
	return 0;
}