（数据结构）单链表 —— 尾插，尾删，头插，头删，查找，插入，删除。

1.创建结点

//创建结点
SLTNode* BuySLTNode(SListDataType x)
{
    SLTNode* newnode = (SLTNode*)malloc(sizeof(SLTNode));
    newnode->data = x;
    newnode->next = NULL;
    return newnode;
}

2.打印

// 打印
void SListPrint(SLTNode* phead)
{
    SLTNode* cur = phead;
    while (cur != NULL)
    {
        printf("%d->", cur->data);
        cur = cur->next;
    }
    printf("NULL\n");
}

3.尾插

//尾插
void SListPushBack(SLTNode** pphead, SListDataType x)
{

    //1.要插入一个结点 首先要malloc一个结点
    SLTNode* newnode = (SLTNode*)malloc(sizeof(SLTNode));
    newnode->data = x;   //创建后要初始化
    newnode->next = NULL; 
    //2.如果链表无结点 就把newnode直接做表头
    if (*pphead == NULL)
    {
        *pphead = newnode;
    }
    //3.如果链表有结点 找到尾
    else
    {
        SLTNode* tail = *pphead;//尾
        while (tail->next != NULL)
        {
            tail = tail->next;  //尾一直找到最后一个节点
        }
        tail->next = newnode;   //最后一个结点的next为newnode

    }
}

4.头插

//头插
void SListPushFront(SLTNode** pphead, SListDataType x)
{
    //也要创建一个结点
    SLTNode* newnode = BuySLTNode(x);
    //newnode->next 存放第一个结点 把表头改为newnode
    newnode->next = *pphead;
    *pphead = newnode;
}

5.头删

//头删
void SListPopFront(SLTNode** pphead)
{
    if (*pphead == NULL)
    {
        return;
    }                        //不能上来直接free头
    SLTNode* tmp = *pphead;  //先存链表头 一会free
    *pphead = (*pphead)->next;//把头换到下一个
    free(tmp);
}

6.尾删

//尾删
void SListPopBack(SLTNode** pphead)
{
    if (*pphead == NULL)
    {
        return;
    }
    else if ((*pphead)->next == NULL)
    {
        free(*pphead); //把pList指向的那块内存空间释放
        *pphead = NULL;//把pList指针置为空
    }
    else
    {
        SLTNode* tail = *pphead; //尾删 需要知道尾和尾前的结构体(置为空)
        SLTNode* prev = NULL;
        while (tail->next != NULL)
        {
            prev = tail;   //小跟班指针
            tail = tail->next;
        }
        free(tail);
        prev->next = NULL;
    }

}

7.查找

//查找
SLTNode* SListFind(SLTNode* phead, SListDataType x)
{
    SLTNode* cur = phead;
    while (cur != NULL)
    {
        if (cur->data == x)
        {
            return cur;
        }
        cur = cur->next;
    }
    return NULL;
}

8.在pos前面插入x

//在pos前面插入x
void SListInsert(SLTNode** pphead, SLTNode* pos, SListDataType x)
{
    SLTNode* newnode = BuySLTNode(x);
    if (*pphead == pos)
    {
        newnode->next = *pphead;
        *pphead = newnode;
    }
    else
    {
        SLTNode* cur = *pphead;
        while (cur->next != pos)
        {
            cur = cur->next;
        }
        newnode->next = pos;
        cur->next = newnode;
    }
}

9.删除pos位置的值

//删除pos位置的值
void SListErase(SLTNode** pphead, SLTNode* pos)
{
    if (pos == *pphead)
    {
        void SListPopFront(SLTNode * *pphead);
    }
    else
    {
        SLTNode* cur = *pphead;
        while (cur->next != pos)
        {
            cur = cur->next;
        }
        cur->next = pos->next;
        free(pos);
    }
}

10.头文件

#pragma once
#include<stdio.h>
#include<stdlib.h>
typedef int SListDataType; //重命名data类型 以后要改char double 直接就改

typedef struct SListNode
{
    SListDataType data;
    struct SListNode* next;
}SLTNode;

//打印
void SListPrint(SLTNode* phead);
//尾插  (可能会改变链表的头指针就要传二级指针)
void SListPushBack(SLTNode** pphead, SListDataType x);//传入一个二级指针链表头 和 插入的数据
//头插 
void SListPushFront(SLTNode** pphead, SListDataType x);
//头删
void SListPopFront(SLTNode** pphead);
//尾删
void SListPopBack(SLTNode** pphead);
//查找
SLTNode* SListFind(SLTNode* phead, SListDataType x);
//在pos前面插入x
void SListInsert(SLTNode** pphead, SLTNode* pos, SListDataType x);
//删除pos位置的值
void SListErase(SLTNode** pphead, SLTNode* pos);

11.测试代码

#define _CRT_SECURE_NO_WARNINGS  1
#include"Slist.h"

void SLTNodeTest1()
{
    SLTNode* Plist = NULL;
    SListPushBack(&Plist, 1);
    SListPushBack(&Plist, 2);
    SListPushBack(&Plist, 3);
    SListPushFront(&Plist, 0);
    //SListPopFront(&Plist);
    //SListPrint(Plist);
    SListPushBack(&Plist, 4);
    //SLTNode* pos = SListFind(Plist, 0);
    //if (pos != NULL)
    //{
    //    SListInsert(&Plist, pos, 30);
    //}
    SListPrint(Plist);
    SLTNode* pos = SListFind(Plist, 2);
    if (pos != NULL)
    {
        SListErase(&Plist, pos);
    }
    SListPrint(Plist);
}
int main()
{
    SLTNodeTest1();
    return 0;
}