12.8.6-PointersOnC-20220405

//初始为空的双链表
#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define LENWORD 11
typedef struct node{
	struct node *pfwd;
	struct node *pbwd;
	char value[LENWORD];
}Node;
char *my_fgets(char *p,int n);//读取输入
void ClearList(Node **plist);//清空链表
int AddList(Node **plist);//添加节点
void ShowList(Node *plist);//显示链表
Node *Search(Node **plist);//12.8.6查找节点
int Remove(Node **plist,Node *pnode);//12.8.6删除节点
int main(){
	Node *pdata=NULL;
	ClearList(&pdata);
	for(;AddList(&pdata)==1;);
	if(pdata) ShowList(pdata);
	for(;Remove(&pdata,Search(&pdata));ShowList(pdata));
	ClearList(&pdata);
return 0;}
//
char *my_fgets(char *p,int n){
	char ch=0,*input=NULL,*found=NULL;
	if(input=fgets(p,n,stdin))
		if(found=strchr(input,10)) *found=0;
		else while((ch=getchar())!=EOF&&ch!=10);
return input;}

void ClearList(Node **plist){
	for(Node *ptemp=NULL;*plist;){
		ptemp=*plist;
		*plist=(*plist)->pfwd;
		free(ptemp);
	}
}

int AddList(Node **plist){
	char input[LENWORD]={0};
	Node **proot=plist;
	fputs("Input the word(EnterQuit):->",stdout);
	if(my_fgets(input,LENWORD)&&*input){//输入不为NULL或者Enter
		Node *pcall=NULL;
		if(!(pcall=(Node *)calloc(1,sizeof(Node)))) return -1;
		strncpy(pcall->value,input,LENWORD);//拷贝字符串
		for(;(pcall->pfwd=*plist)&&strcmp(input,(*plist)->value)>=0;plist=&(*plist)->pfwd);//查找插入位置
		if(*plist){//新项为非末项
			pcall->pbwd=(*plist)->pbwd;//退挂钩
			(*plist)->pbwd=pcall;//进项退挂钩
		}
		else{//新项为末项或唯一项
			if(*plist!=*proot){//新项为末项
				pcall->pbwd=(*proot)->pbwd;//退挂钩	
				(*proot)->pbwd=pcall;//首项退挂钩
			}
			else pcall->pbwd=NULL;//新项为唯一项,退挂钩
		}
		*plist=pcall;//退项进挂钩
	}
	else return 0;
return 1;}

void ShowList(Node *plist){
	char num[LENWORD]={0};//不能在for中创建
	for(int i=0;plist;plist=plist->pfwd,i++){
		printf("NO.%d:%s\n",i+1,plist->value);
	}
}

Node *Search(Node **plist){
	char input[LENWORD]={0};
	fputs("Input the word(EnterQuit):->",stdout);
	if(!my_fgets(input,LENWORD)||!*input) return NULL;//输入为NULL或者Enter
	else for(;*plist&&strcmp(input,(*plist)->value);plist=&(*plist)->pfwd);
return *plist;}

int Remove(Node **plist,Node *pnode){
	if(!*plist||!pnode) return 0;
	Node **proot=plist;
	for(;*plist!=pnode;plist=&(*plist)->pfwd);
	if(!pnode->pfwd){if(*proot!=*plist) (*proot)->pbwd=pnode->pbwd;}//末项,首项退挂钩
	else pnode->pfwd->pbwd=pnode->pbwd;//非末项或唯一项,进项退挂钩
	*plist=pnode->pfwd;//退项进挂钩
	if(!*proot) return 0;//链表为空
return 1;}