（数据结构）单链表 —— 尾插，尾删，头插，头删，查找，插入，删除。

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

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

//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
 
  }
}

//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;
}

//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);
}

//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;
  }
 
}

//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;
}

//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;
  }
}

//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);
  }
}

#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);

#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;
}