(含有头指针以及尾指针)单链表各类功能的实现

对单链表实现如下功能:

void InitList(List *list);             //初始化单链表
bool push_back(List *list,ElemType x); //尾插法
void show_seqlist(List *list);         //显示链表内容
bool push_front(List *list,ElemType x);//头插法
bool pop_back(List *list);             //尾删法
bool pop_front(List *list);            //头删法
Node *find(List *list,ElemType x);     //查找函数,找到返回指向该元素的指针
bool modify(List *list,ElemType x);    //修改某一元素的值
void delete_val(List *list,ElemType x);//按值删除
void clear(List *list);                //清空链表
void destroy(List *list);              //销毁链表
int  length(List *list);               //求链表长度
void resver(List *list);               //逆至链表
void prio(List *list,ElemType x);      //求某个值的前驱
void next(List *list,ElemType x);      //求某个值的后继


List.h:

#ifndef __LIST_H__
#define __LIST_H__

#include<assert.h>
#include<iostream>
using namespace std;
typedef int ElemType;

typedef struct Node
{
	ElemType data;
	struct Node *next;
}Node;

typedef struct List
{
	Node *first;
	Node *last;
	int size;
}List;

void InitList(List *list);             //初始化单链表
bool push_back(List *list,ElemType x); //尾插法
void show_seqlist(List *list);         //显示链表内容
bool push_front(List *list,ElemType x);//头插法
bool pop_back(List *list);             //尾删法
bool pop_front(List *list);            //头删法
Node *find(List *list,ElemType x);     //查找函数,找到返回指向该元素的指针
bool modify(List *list,ElemType x);    //修改某一元素的值
void delete_val(List *list,ElemType x);//按值删除
void clear(List *list);                //清空链表
void destroy(List *list);              //销毁链表
int  length(List *list);               //求链表长度
void resver(List *list);               //逆至链表
void prio(List *list,ElemType x);      //求某个值的前驱
void next(List *list,ElemType x);      //求某个值的后继
#endif



List.cpp:

#include"List.h"
//初始化单链表
void InitList(List *list)
{
	Node *s = (Node *)malloc(sizeof(Node));
	assert(s != NULL);
	s->next = NULL;
	list->first = list->last = s;
	list->size = 0;
}
//尾插法:开辟并初始化--->>连接---->>指针后移
bool push_back(List *list,ElemType x)
{
	Node *s = (Node *)malloc(sizeof(Node));//开辟一个结点
	if(s == NULL)
	{
		return false;
	}
	s->next = NULL;//对节点的初始化
	s->data = x;
	
	list->last->next = s;//连接
	list->last = s;      //后移(尾指针后移)
	list->size++;
	return true;
}
//打印链表的内容
void show_seqlist(List *list)
{
	Node *p = list->first->next;
	while(p != NULL)
	{
		cout<<p->data<<"--->";
		p = p->next;
	}
	cout<<"NULL"<<endl;
}
//头插法:开辟并初始化--->>连接---->>指针后移  !!注意特殊情况!!
bool push_front(List *list,ElemType x)
{
	Node *s = (Node *)malloc(sizeof(Node));
	if(s == NULL)
	{
		return false;
	}
	s->data = x;
	s->next = list->first->next;
	list->first->next = s;
//注意:如果是第一个结点,则尾指针需要改变指向即指向第一个结点
//(不再指向头)如果不是第一个结点,尾指针指向无需改变 
	if(list->size == 0)
	{
		list->last = s;
	}
	list->size++;
	return true;
}
//尾删法:找到最后一个节点的前驱(指向赋空)---->尾指针指向它--->size - 1
bool pop_back(List *list)
{
	if(list->size == 0)
	{
		cout<<"链表已空"<<endl;
		return false;
	}
	Node *pre = list->first;
	while(pre->next != list->last)//找到要删除节点(最后一个结点)的前驱
	{
		pre = pre->next;
	}
	pre->next = NULL;//因为该前驱要作为尾结点,所以其指针域得赋空
	free(list->last);//释放要删除的结点
	list->last = pre;//尾指针指向改变
	
/*	pre->next = NULL;
	list->last = pre;

	free(pre);
	pre = NULL;
//	free(list->last);*/
	
	list->size--;
	return true;
}
//free(p)作用是:释放p所指向的空间,而非释放指针p!!!!!
//动态开辟的空间才需要手工释放,其他的空间系统自动回收

//头删法:释放第一个节点->size-1(如果只有一个节点,释放它之后尾指针得指向头结点),其他情况尾指针不变
bool pop_front(List *list)
{
	if(list->size == 0)
	{
		cout<<"链表已空"<<endl;
		return false;
	}
	Node *p = list->first->next;//p指向要释放的第一个节点
	list->first->next = p->next;//头指针指向下一个节点
	free(p);                    //释放第一个节点
	if(list->size == 1)         
	{
		list->last = list->first;//如果只有一个节点,释放它之后尾指针得指向头结点),其他情况尾指针不变
	}
	list->size--;
	return true;
}
//查找函数

/*Node *find(List *list,ElemType x)
{
	Node *p = list->first->next;//p指向第一个节点
	while(p != NULL)
	{
		if(x == p->data)
			return p;
		else
			p = p->next;
	}
	return NULL;
}*/
Node *find(List *list,ElemType x)
{
	Node *p = list->first->next;//p指向第一个节点
	while(p!=NULL && p->data!= x)
	{
		p = p->next;
	}
	return p;//while循环退出条件:没找到则-->p=NULL,找到p为指向所寻找节点的指针
}
//修改函数
bool modify(List *list,ElemType x)
{
	ElemType item;
	Node *p = find(list,x);
	if(p != NULL)
	{
		cout<<"Please input the new value:"<<endl;
		cin>>item;
		p->data = item;
		cout<<"it is modified"<<endl;
		return true;
	}
	else
		cout<<"it's not exist!"<<endl;
}
//按值删除结点
void delete_val(List *list,ElemType x)
{
	Node *p = find(list,x);      //找到要删除的结点
	if(p != NULL)
	{
		if(p == list->first->next)//如果是第一个结点(头删法)
		{
			pop_front(list);
		}
		else if(p == list->last)  //如果是最后一个结点(尾删法)
		{
			pop_back(list);
		}
		else //既不是第一个结点,也不是最后一个节点
		{
			p->data = p->next->data;//将要删除的结点的data赋值为下一个节点的data
			p->next = p->next->next;//连接
			free(p->next);          //将要删除的结点的下一个结点释放
		}
		/*else //既不是第一个结点,也不是最后一个节点
		{
			Node *pre = list->first;
			while(pre->next != p)//找到要删除节点的前驱
			{
				pre = pre->next;
			}
			pre->next = p->next;//连接
			free(p);            //释放要删除的结点
		}*/
		list->size--;
		cout<<"it is deleted!"<<endl;
	}
	else
	{
		cout<<"it is not exist!"<<endl;
	}

}
//清空单链表
/*void clear(List *list,ElemType x)
{
	for(int i=0;i<list->size;++i)
	{
		pop_back(list);//或者pop_front(list)
	}
}*/
void clear(List *list)
{
	Node *p = list->first->next;//p指向第一个节点
	while(p != NULL)
	{
		list->first->next = p->next;//分离出第一个结点
		free(p);//将第一个节点释放
		p = list->first->next;//又指向第一个节点(连续删除第一个结点)
	}
	list->last = list->first; //尾指针以及头指针都指向头结点
	list->size = 0;
}
//销毁链表
void destroy(List *list)
{
	clear(list);//清空链表
	free(list->first);//头结点释放
	list->first = list->last = NULL;//头(尾)指针赋空,防止成为野指针
}
//求链表长度
int length(List *list)
{
	return list->size;
}
//链表逆至
/*改变指针的指向*/
void resver(List *list)
{
	Node *pre = list->first->next;//pre指向第一个节点
	Node *p = pre->next;          //  p指向第二个结点
	pre->next = NULL;             //逆序之后第一个节点成为最后一个节点,所以next=NULL
	while(p != NULL)
	{
		Node *pre1 = pre;//将当前的指向保存下来
		Node *p1 = p;

		pre = p; //为下一次(第n-1次)交换做准备(必须在指向改变之后进行!!!!!)
		p = p->next;

		p1->next = pre1;//交换当前两个(第n次)后一个指向前一个
	}
	list->first->next = pre;    //退出循环,p=NULL,pre指向原来的最后一个结点(逆序后成为第一个)
	
}
/*交换值*/
/*void resver(List *list)
{
	Node *left = list->first->next;
	Node *right = list->last;
	Node *p = list->first;
	while(left != right)
	{
		left->data  = left->data + right->data;//对称的两个数交换
		right->data = left->data - right->data;
		left->data  = left->data - right->data;

		while(p->next != right)//找到倒数第二个结点
		{
			p = p->next;
		}

		right = p;//为下一次交换做准备
		left = left->next;	
	}
}*/
//求某个值的前驱
void prio(List *list,ElemType x)
{
	Node *p = find(list,x);
	if(p == NULL)
	{
		cout<<"it is not exist!\n"<<endl;
	}
	if(p == list->first->next)
	{
		cout<<"it does not have next"<<endl;
	}
	else
	{
		Node *pre = list->first;
		while(pre->next != p)
		{
			pre = pre->next;
		}
		cout<<"it's prio is found"<<endl;
		cout<<"it is"<<pre->data<<endl;;
	}
}
//求某个值的后继
void next(List *list,ElemType x)
{
	Node *p = find(list,x);
	if(p == NULL)
	{
		cout<<"it is not exist!\n"<<endl;
	}
	if(p == list->last)
	{
		cout<<"it does not have next"<<endl;
	}
	else
	{
		cout<<"it's next is found"<<endl;
		cout<<"it is"<<p->next->data<<endl;
	}
}
main.cpp:

#include"List.h"
void main()
{
	List mylist;
	InitList(&mylist);

	int select = 1;
	ElemType item;
	Node *p = NULL;

	while(select)
	{
		cout<<"**********************************"<<endl;
		cout<<"* [1] push_back   [2] push_front *"<<endl;
		cout<<"* [3] show_seqlist[0] quit_system*"<<endl;
		cout<<"* [4] pop_back    [5] pop_front  *"<<endl;
		cout<<"* [6] find                       *"<<endl;
		cout<<"* [7] modify      [8] clear      *"<<endl;
		cout<<"* [9] destroy     [10]delete_val *"<<endl;
		cout<<"* [11] resver     [12]length     *"<<endl;
		cout<<"* [13] prio       [14]next       *"<<endl;
		cout<<"**********************************"<<endl;
		cout<<"请选择:>";
		cin>>select;
		switch(select)
		{
		case 1:
			cout<<"请输入要插入的数据(-1结束):>";
			while(cin>>item,item!=-1)
			{
				push_back(&mylist,item);
			}
			break;
		case 2:
			cout<<"请输入要插入的数据(-1结束):>";
			while(cin>>item,item!=-1)
			{
				push_front(&mylist,item);
			}
			break;
		case 3:
			show_seqlist(&mylist);
			break;
		case 4:
			pop_back(&mylist);
			break;
		case 5:
			pop_front(&mylist);	
			break;
		case 6:
			cout<<"输入你要查找的值:";
			cin>>item;
			p =find(&mylist,item);
			if(p != NULL)
				cout<<"it is found!"<<endl;
			else
				cout<<"it is not exit!"<<endl;
			break;
		case 7:
			cout<<"请输入要修改的值:";
			cin>>item;
			modify(&mylist,item);
			break;
		case 8:
			clear(&mylist);
			break;
		case 9:
			destroy(&mylist);
			break;
		case 10:
			cout<<"请输入要删除的值:";
			cin>>item;
			delete_val(&mylist,item);
			break;
		case 11:
			resver(&mylist);
			break;
		case 12:
			{
				int n = length(&mylist);
				cout<<"the length of the list is:"<<n<<endl;
			}
			break;
		case 13:
			cout<<"输入你要查找前驱的值:";
			cin>>item;
			prio(&mylist,item);
			break;
		case 14:
			cout<<"输入你要查找后继的值:";
			cin>>item;
			next(&mylist,item);
			break;
		default:
			break;
		}
	}
	destroy(&mylist);//函数调用完之后,自动销毁链表
}





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