# 线性表的链表的增删查改等的操作

线性表的链表的增删查改等的操作

#include<stdio.h>
//d定义类型
typedef int LDateType;
//定义结构体类型
typedef struct listNode
{
    LDateType _date;
    struct listNode* _next;
}listNode;
//定义头指针
typedef struct list
{
    listNode* _head;
}list;
//初始化头指针
void InistList(list* lst)
{
    if (lst == NULL)
        return;
    //初始化为空的链表
    lst->_head = NULL;
}
listNode* creatNode(LDateType val)
{
    listNode* node = (listNode*)malloc(sizeof(listNode));
    node->_date = val;
    node->_next = NULL;
    return node;
}
//尾插
void listPushBack(list* lst, LDateType val)
{
    if (lst == NULL)
        return;
    //空链表插入
    if (lst->_head==NULL)
    {
        lst->_head = creatNode(val);
    }
    //非空链表尾插
    else
    {
        listNode* tail = lst->_head;
        while (tail->_next != NULL)
        {
            tail = tail->_next;
        }
        tail->_next = creatNode(val);
    }

}
//尾删
void listPopBack(list* lst)
{
    if (lst == NULL||lst->_head==NULL)return;
    struct listNode* tail = lst->_head;
    struct listNode* prev = NULL;
    while (tail->_next != NULL)
    {
        prev = tail->_next;
        tail = tail->_next;
    }
    //删除节点
    free(tail);
    //修改指向
    if (prev == NULL)//删除的为头结点，更新头结点
        lst->_head = NULL;
    else
    prev->_next = NULL;
}
//头插
void listPushFront(list* lst, LDateType val)
{
    if (lst == NULL)return;
    //空的链表，插入第一个数据
    if (lst->_head == NULL)
        lst->_head = creatNode(val);
    else
    {
        listNode* node = creatNode(val);
        listNode* next = lst->_head;
        lst->_head = node;
        node->_next = next;
    }
}
//头删
void listPopFront(list *lst)
{
    if (lst == NULL || lst->_head == NULL)return; 
    listNode* next = lst->_head->_next;
    //释放头结点
    free(lst->_head);
    lst->_head = next;
}
//第一个元素后后插入
void listInsertAfter(listNode* cur, LDateType val)
{
    listNode* node = creatNode(val);
    listNode* next = cur->_next;
    cur->_next = node;
    node->_next = next;
}
//删除第二个元素
void listEraseAfter(listNode* cur)
{
    listNode* next = cur->_next;
    if (next == NULL)return;
    listNode* nextnext = next->_next;
    free(next);
    cur->_next=nextnext;
}
//查找值为val，返回地址
listNode* listFind(list* lst,LDateType val)
{
    if (lst == NULL || lst->_head == NULL)return;
    //从第一个值开始遍历
    listNode* cur = lst->_head;
    while (cur)
    {
        if (cur->_date == val)
            return cur;
        cur = cur->_next;
    }
    return NULL;
}
//求链表的大小
int listSize(list* lst)
{
    if (lst == NULL)return;
    int count = 0;
    listNode* next = lst->_head;
    while (next)
    {
        next = next->_next;
        count++;
    }
    return count;
}
//销毁链表
void listDestroy(list* lst)
{
    if (lst == NULL||lst->_head==NULL)return;
    listNode*  ps = lst->_head,*next = NULL;
    while (ps)
    {
        next = ps->_next;
        free(ps);
        ps = next;
    }
    lst->_head = NULL;

}