链表的概念及结构
概念:链表是一种物理存储结构上非连续、非顺序的存储结构,数据元素的逻辑顺序是通过链表 中的指针链接次序实现的
链表的分类
实际中链表的结构非常多样,以下情况组合起来就有8种链表结构:
-
单向或者双向
-
带头或者不带头
-
循环或者非循环
虽然有这么多的链表的结构,但是我们实际中最常用还是两种脑结构:
- 无头单向非循环链表:结构简单,一般不会单独用来存数据。实际中更多是作为其他数据结 构的子结构,如哈希桶、图的邻接表等等。另外这种结构在笔试面试中出现很多。
- 带头双向循环链表:结构最复杂,一般用在单独存储数据。实际中使用的链表数据结构,都是带头双向循环链表。另外这个结构虽然结构复杂,但是使用代码实现以后会发现结构会带 来很多优势,实现反而简单了,后面我们代码实现了就知道了。
单链表的实现
无头+单向+非循环链表增删查改实现
无头+单向+非循环链表增删查改实现代码:
#pragma once
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>
typedef int SLNDataType;
typedef struct SListNode
{
int val;
struct SListNode* next;
}SLNode;
//打印
void SLTPrint(SLNode* phead);
//尾插
void SLTPushBack(SLNode** pphead, SLNDataType x);
//头插
void SLTPushFront(SLNode** pphead, SLNDataType x);
//尾删
void SLTPopBack(SLNode** pphead);
//头删
void SLTPopFront(SLNode** pphead);
SLNode* SLTFind(SLNode* phead, SLNDataType x);
// 在pos的前面插入
SLNode* SLTInsert(SLNode** pphead, SLNode* pos, SLNDataType x);
// 删除pos位置
void SLTErase(SLNode** pphead, SLNode* pos);
// 后面插入 后面删除
void SLTInsertAfter(SLNode* pos, SLNDataType x);
void SLTEraseAfter(SLNode* pos);
// 前面插入
void SLTInsertHead(SLNode* pos, SLNDataType x);
//销毁
void SLTDestroy(SLNode** pphead);
#define _CRT_SECURE_NO_WARNINGS
#include"SList.h"
void SLTPrint(SLNode* phead)
{
SLNode* cur = phead;
while (cur != NULL)
{
printf("%d ->", cur->val);
cur = cur->next;
}
printf("NULL");
}
SLNode* CreateNode(SLNDataType x)
{
SLNode* newnode = (SLNode*)malloc(sizeof(SLNode));
if (newnode == NULL)
{
perror("malloc fail");
exit(-1);
}
newnode->val = x;
newnode->next = NULL;
return newnode;
}
void SLTPushBack(SLNode** pphead, SLNDataType x)
{
SLNode* newnode = CreateNode(x);
if (*pphead == NULL)
{
*pphead = newnode;
}
else
{
SLNode* tail = *pphead;
while (tail->next != NULL)
{
tail = tail->next;
}
SLNode* newnode = CreateNode(x);
tail->next = newnode;
}
}
void SLTPushFront(SLNode** pphead, SLNDataType x)
{
SLNode* newnode = CreateNode(x);
newnode->next = *pphead;
*pphead = newnode;
}
void SLTPopBack(SLNode** pphead)
{
assert(*pphead);
if ((*pphead)->next == NULL)
{
free(*pphead);
*pphead = NULL;
}
else
{
//方法1:
/*SLNode* tail = *pphead;
while (tail->next->next != NULL)
{
tail = tail->next;
}
free(tail->next);
tail->next = NULL;*/
//方法2:
SLNode* tail = *pphead;
SLNode* prev = NULL;
while (tail != NULL)
{
prev = tail;
tail = tail->next;
}
free(tail);
tail = NULL;
prev->next = NULL;
}
}
void SLTPopFront(SLNode** pphead)
{
assert(*pphead);
//方法1:
/*SLNode* tmp = *pphead;
*pphead = tmp->next;
free(tmp);
tmp = NULL;*/
//方法2:
/*SLNode* tmp = *pphead;
*pphead = (*pphead)->next;
free(tmp);*/
//错误:
//SLNode* tmp = *pphead;
//free(tmp);
//*pphead = (*pphead)->next;
//这里先free(tmp)会导致*pphead后面存放的数据无法拿取,造成内存泄露
//方法3:
SLNode* tmp = (*pphead)->next;
free(*pphead);
*pphead = tmp;
}
SLNode* SLTFind(SLNode* phead, SLNDataType x)
{
SLNode* cur = phead;
while (cur)
{
if (cur->val == x)
{
return cur;
}
else
{
cur = cur->next;
}
}
return NULL;
}
SLNode* SLTInsert(SLNode** pphead, SLNode* pos, SLNDataType x)
{
assert(pphead);
assert(*pphead);
assert(pos);
if (pos == *pphead)
{
//头插
SLTPushFront(pphead, x);
}
else
{
SLNode* prev = *pphead;
while (prev)
{
if (prev->next != pos)
{
prev = prev->next;
}
else
{
SLNode* newnode = CreateNode(x);
newnode->next = pos;
prev->next = newnode;
}
}
while (prev->next != pos)
{
prev = prev->next;
}
SLNode* newnode = CreateNode(x);
newnode->next = pos;
prev->next = newnode;
}
}
void SLTErase(SLNode** pphead, SLNode* pos)
{
assert(pphead);
assert(*pphead);//不允许链表为空
assert(pos);//pos必需为有效节点
if (*pphead == pos)
{
SLTPopFront(pphead);
}
else
{
SLNode* prev = *pphead;
while (prev->next != pos)
{
prev = prev->next;
}
prev->next = pos->next;
free(pos);
pos = NULL;
}
}
void SLTInsertAfter(SLNode* pos, SLNDataType x)
{
assert(pos);
SLNode* newnode = (SLNode*)malloc(sizeof(SLNode));
newnode->next = pos->next;
pos->next = newnode;
newnode->val = x;
}
void SLTEraseAfter(SLNode* pos)
{
assert(pos);
assert(pos->next);
SLNode* tmp = pos->next;
pos->next = pos->next->next;
free(tmp);
tmp = NULL;
}
void SLTInsertHead(SLNode* pos, SLNDataType x)
{
SLNode* newnode = (SLNode*)malloc(sizeof(SLNode));
newnode->val = pos->val;
newnode->next = pos->next;
pos->val = x;
pos->next = newnode;
}
void SLTDestroy(SLNode** pphead)
{
assert(pphead);
SLNode* cur = *pphead;
while (cur)
{
SLNode* tmp = cur->next ;
free(cur);
cur = tmp;
}
*pphead = NULL;
}
#define _CRT_SECURE_NO_WARNINGS
#include"SList.h"
void TestSLT1()
{
SLNode* plist = NULL;
SLTPushBack(&plist, 1);
SLTPushBack(&plist, 2);
SLTPushBack(&plist, 3);
SLTPrint(plist);
printf("\n");
SLTPushFront(&plist, 4);
SLTPushFront(&plist, 5);
SLTPrint(plist);
printf("\n");
}
void TestSLT2()
{
SLNode* plist = NULL;
SLTPushBack(&plist, 1);
SLTPushBack(&plist, 2);
SLTPushBack(&plist, 3);
SLTPushBack(&plist, 4);
SLTPushBack(&plist, 5);
SLTPrint(plist);
printf("\n");
SLTPopBack(&plist);
SLTPopBack(&plist);
SLTPopBack(&plist);
SLTPrint(plist);
}
void TestSLT3()
{
SLNode* plist = NULL;
SLTPushBack(&plist, 1);
SLTPushBack(&plist, 2);
SLTPushBack(&plist, 3);
SLTPushBack(&plist, 4);
SLTPushBack(&plist, 5);
SLTPrint(plist);
printf("\n");
SLTPopFront(&plist);
SLTPopFront(&plist);
SLTPrint(plist);
printf("\n");
SLNode* pos = SLTFind(plist, 4);
SLTInsert(&plist, pos, 30);
SLTInsert(&plist, pos, 40);
SLTPrint(plist);
printf("\n");
}
void TestSLT4()
{
SLNode* plist = NULL;
SLTPushBack(&plist, 1);
SLTPushBack(&plist, 2);
SLTPushBack(&plist, 3);
SLTPushBack(&plist, 4);
SLTPrint(plist);
printf("\n");
SLNode* pos = SLTFind(plist, 2);
SLTErase(&plist, pos);
SLTPrint(plist);
printf("\n");
pos = SLTFind(plist, 3);
SLTInsertAfter(pos, 5);
SLTPrint(plist);
printf("\n");
pos = SLTFind(plist, 1);
SLTEraseAfter(pos);
SLTPrint(plist);
printf("\n");
SLTDestroy(&plist);
}
void TestSLT5()
{
SLNode* plist = NULL;
SLTPushBack(&plist, 1);
SLTPushBack(&plist, 2);
SLTPushBack(&plist, 3);
SLTPushBack(&plist, 4);
SLTPrint(plist);
printf("\n");
SLNode* pos = SLTFind(plist, 2);
SLTInsertHead(pos, 20);
SLTPrint(plist);
printf("\n");
SLTDestroy(&plist);
}
int main()
{
TestSLT5();
return 0;
}
无头+单向+非循环链表增删查改实现思路:
新建结点:
SLNode* CreateNode(SLNDataType x);
SLNode* CreateNode(SLNDataType x)
{
SLNode* newnode = (SLNode*)malloc(sizeof(SLNode));
if (newnode == NULL)
{
perror("malloc fail");
exit(-1);
}
newnode->val = x;
newnode->next = NULL;
return newnode;
}
尾插:
void SLTPushBack(SLNode** pphead, SLNDataType x);
void SLTPushBack(SLNode** pphead, SLNDataType x)
{
SLNode* newnode = CreateNode(x);
if (*pphead == NULL)
{
*pphead = newnode;
}
else
{
SLNode* tail = *pphead;
while (tail->next != NULL)
{
tail = tail->next;
}
SLNode* newnode = CreateNode(x);
tail->next = newnode;
}
}
头插:
void SLTPushFront(SLNode** pphead, SLNDataType x);
void SLTPushFront(SLNode** pphead, SLNDataType x)
{
SLNode* newnode = CreateNode(x);
newnode->next = *pphead;
*pphead = newnode;
}
尾删:
void SLTPopBack(SLNode** pphead);
void SLTPopBack(SLNode** pphead)
{
assert(*pphead);
if ((*pphead)->next == NULL)
{
free(*pphead);
*pphead = NULL;
}
else
{
//方法1:
/*SLNode* tail = *pphead;
while (tail->next->next != NULL)
{
tail = tail->next;
}
free(tail->next);
tail->next = NULL;*/
//方法2:
SLNode* tail = *pphead;
SLNode* prev = NULL;
while (tail != NULL)
{
prev = tail;
tail = tail->next;
}
free(tail);
tail = NULL;
prev->next = NULL;
}
}
头删:
void SLTPopFront(SLNode** pphead);
void SLTPopFront(SLNode** pphead)
{
assert(*pphead);
//方法1:
/*SLNode* tmp = *pphead;
*pphead = tmp->next;
free(tmp);
tmp = NULL;*/
//方法2:
/*SLNode* tmp = *pphead;
*pphead = (*pphead)->next;
free(tmp);*/
//错误:
//SLNode* tmp = *pphead;
//free(tmp);
//*pphead = (*pphead)->next;
//这里先free(tmp)会导致*pphead后面存放的数据无法拿取,造成内存泄露
//方法3:
SLNode* tmp = (*pphead)->next;
free(*pphead);
*pphead = tmp;
}
在pos的前面插入:
SLNode* SLTInsert(SLNode** pphead, SLNode* pos, SLNDataType x);
SLNode* SLTInsert(SLNode** pphead, SLNode* pos, SLNDataType x)
{
assert(pphead);
assert(*pphead);
assert(pos);
if (pos == *pphead)
{
//头插
SLTPushFront(pphead, x);
}
else
{
SLNode* prev = *pphead;
while (prev->next != pos)
{
prev = prev->next;
}
SLNode* newnode = CreateNode(x);
newnode->next = pos;
prev->next = newnode;
}
}
错误思路:
删除pos位置:
void SLTErase(SLNode** pphead, SLNode* pos);
void SLTErase(SLNode** pphead, SLNode* pos)
{
assert(pphead);
assert(*pphead);//不允许链表为空
assert(pos);//pos必需为有效节点
if (*pphead == pos)
{
SLTPopFront(pphead);
}
else
{
SLNode* prev = *pphead;
while (prev->next != pos)
{
prev = prev->next;
}
prev->next = pos->next;
free(pos);
pos = NULL;
}
}
pos后面插入:
void SLTInsertAfter(SLNode* pos, SLNDataType x);
void SLTInsertAfter(SLNode* pos, SLNDataType x)
{
assert(pos);
SLNode* newnode = (SLNode*)malloc(sizeof(SLNode));
newnode->next = pos->next;
pos->next = newnode;
newnode->val = x;
}
pos后面删除
void SLTEraseAfter(SLNode* pos);
void SLTEraseAfter(SLNode* pos)
{
assert(pos);
assert(pos->next);
SLNode* tmp = pos->next;
pos->next = pos->next->next;
free(tmp);
tmp = NULL;
}
带头+双向+循环链表增删查改实现
带头+双向+循环链表增删查改实现代码:
#pragma once
#include<stdio.h>
#include<assert.h>
#include<stdlib.h>
typedef int LTDataType;
typedef struct ListNode
{
struct ListNode* prev;
struct ListNode* next;
LTDataType val;
}LTNode;
LTNode* LTInit();//初始化
void LTPrint(LTNode* phead);//打印
void LTPushBack(LTNode* phead, LTDataType x);//尾插
void LTPopBack(LTNode* phead);//尾删
void LTPushFront(LTNode* phead, LTDataType x);//头插
void LTPopFront(LTNode* phead);//头删
LTNode* LTFind(LTNode* phead, LTDataType x);
//在pos前面的插入
void LTInisert(LTNode* pos, LTDataType x);
//删除pos位置
void LTErase(LTNode* pos);
void LTDestroy(LTNode* phead);
#define _CRT_SECURE_NO_WARNINGS 1
#include"List.h"
LTNode* CreateLTNode(LTDataType x)
{
LTNode* newnode = (LTNode*)malloc(sizeof(LTNode));
if (newnode == NULL)
{
perror("malloc fail");
exit(-1);
}
newnode->next = NULL;
newnode->prev = NULL;
newnode->val = x;
return newnode;
}
LTNode* LTInit()
{
LTNode* head = CreateLTNode(-1);
head->next = head;
head->prev = head;
return head;
}
void LTPrint(LTNode* phead)
{
assert(phead);
printf("哨兵位<=>");
LTNode* cur = phead->next;
while (cur != phead)
{
printf("%d<=> ", cur->val);
cur = cur->next;
}
printf("\n");
}
void LTPushBack(LTNode* phead, LTDataType x)
{
//assert(phead);
//LTNode* tail = phead->prev;
//LTNode* newnode = CreateLTNode(x);
//tail->next = newnode;
//newnode->prev = tail;
//newnode->next = phead;
//phead->prev = newnode;
LTInisert(phead, x);
}
void LTPopBack(LTNode* phead)
{
assert(phead);
assert(phead->next != phead);
//LTNode* tail = phead->prev;
//LTNode* tailPrev = tail->prev;
//phead->prev = tailPrev;
//tailPrev->next = phead;
//free(tail);
//tail = NULL;
LTErase(phead->prev);
}
void LTPushFront(LTNode* phead, LTDataType x)
{
assert(phead);
//LTNode* newnode = CreateLTNode(x);
//LTNode* next = phead->next;
//phead->next = newnode;
//newnode->prev = phead;
//newnode->next = next;
//next->prev = newnode;
LTInisert(phead->next, x);
}
void LTPopFront(LTNode* phead)
{
assert(phead);
assert(phead->next !=phead);
//LTNode* first = phead->next;
//LTNode* second = first->next;
//phead->next = second;
//second->prev = phead;
//free(first);
//first = NULL;
LTErase(phead->next );
}
LTNode* LTFind(LTNode* phead, LTDataType x)
{
assert(phead);
LTNode* cur = phead->next;
while (cur != phead)
{
if (cur->val == x)
return cur;
cur = cur->next;
}
return NULL;
}
void LTInisert(LTNode* pos, LTDataType x)
{
assert(pos);
LTNode* newnode = CreateLTNode(x);
LTNode* posPrev = pos->prev;
posPrev->next = newnode;
newnode->prev = posPrev;
newnode->next = pos;
pos->prev = newnode;
}
//void LTErase(LTNode* pos)
//{
// pos->prev->next = pos->next;
// pos->next->prev = pos->prev;
// free(pos);
//}
void LTErase(LTNode* pos)
{
LTNode* posPrev = pos->prev;
LTNode* posNext = pos->next;
posPrev->next = posNext;
posNext->prev = posPrev;
free(pos);
}
void LTDestroy(LTNode* phead)
{
LTNode* cur = phead->next;
while (cur != phead)
{
LTNode* next = cur->next;
free(cur);
cur = next;
}
free(phead);
}
#define _CRT_SECURE_NO_WARNINGS 1
#include"List.h"
//尾插尾删
void TestList1()
{
LTNode* plist = LTInit();
LTPushBack(plist, 1);
LTPushBack(plist, 2);
LTPushBack(plist, 3);
LTPushBack(plist, 4);
LTPrint(plist);
LTPopBack(plist);
LTPopBack(plist);
LTPopBack(plist);
LTPopBack(plist);
LTPrint(plist);
}
void TestList2()
{
LTNode* plist = LTInit();
LTPushFront(plist, 1);
LTPushFront(plist, 2);
LTPushFront(plist, 3);
LTPushFront(plist, 4);
LTPrint(plist);
LTPopFront(plist);
LTPopFront(plist);
LTPrint(plist);
}
void TestList3()
{
LTNode* plist = LTInit();
LTPushBack(plist, 1);
LTPushBack(plist, 2);
LTPushBack(plist, 3);
LTPushBack(plist, 4);
LTPrint(plist);
LTNode* pos = LTFind(plist, 3);
if (pos == NULL)
return 1;
LTInisert(pos, 30);
LTInisert(pos, 40);
LTPrint(plist);
LTErase(pos);
LTPrint(plist);
}
int main()
{
TestList3();
return 0;
}
带头+双向+循环链表增删查改实现思路:
尾插:
void LTPushFront(LTNode* phead, LTDataType x)
{
assert(phead);
//LTNode* newnode = CreateLTNode(x);
//LTNode* next = phead->next;
//phead->next = newnode;
//newnode->prev = phead;
//newnode->next = next;
//next->prev = newnode;
LTInisert(phead->next, x);
}
尾删:
void LTPopBack(LTNode* phead)
{
assert(phead);
assert(phead->next != phead);
//LTNode* tail = phead->prev;
//LTNode* tailPrev = tail->prev;
//phead->prev = tailPrev;
//tailPrev->next = phead;
//free(tail);
//tail = NULL;
LTErase(phead->prev);
}
头插:
void LTPushFront(LTNode* phead, LTDataType x)
{
assert(phead);
//LTNode* newnode = CreateLTNode(x);
//LTNode* next = phead->next;
//phead->next = newnode;
//newnode->prev = phead;
//newnode->next = next;
//next->prev = newnode;
LTInisert(phead->next, x);
}
头删:
void LTPopFront(LTNode* phead)
{
assert(phead);
assert(phead->next !=phead);
//LTNode* first = phead->next;
//LTNode* second = first->next;
//phead->next = second;
//second->prev = phead;
//free(first);
//first = NULL;
LTErase(phead->next );
}
在pos前面的插入
void LTInisert(LTNode* pos, LTDataType x)
{
assert(pos);
LTNode* newnode = CreateLTNode(x);
LTNode* posPrev = pos->prev;
posPrev->next = newnode;
newnode->prev = posPrev;
newnode->next = pos;
pos->prev = newnode;
}
删除pos位置
void LTErase(LTNode* pos)
{
LTNode* posPrev = pos->prev;
LTNode* posNext = pos->next;
posPrev->next = posNext;
posNext->prev = posPrev;
free(pos);
}
顺序表和链表的优势和问题
顺序表优势和问题
顺序表优势: (物理内存连续)
支持下标随机访间。O(1)读取数据的时候内存污染低
顺序表问题:
1、头部或者中间插入删除效率低,要挪动数据。O(N)
2、空间不够需要扩容,扩容有一定的消耗,且可能存在一定的空间浪费
3、只适合尾插尾删
链表优势和问题
链表(双向)优势:
1、任意位置插入删除都是O(1)
2、按需申请释放,合理利用空间,不存在浪费
问题:
1、下标随机访问不方便 O(N))读取数据的时候内存污染高
g-XKGdPylY-1712583804637)]
头删:
void LTPopFront(LTNode* phead)
{
assert(phead);
assert(phead->next !=phead);
//LTNode* first = phead->next;
//LTNode* second = first->next;
//phead->next = second;
//second->prev = phead;
//free(first);
//first = NULL;
LTErase(phead->next );
}
[外链图片转存中…(img-E1GHhRfH-1712583804638)]
在pos前面的插入
void LTInisert(LTNode* pos, LTDataType x)
{
assert(pos);
LTNode* newnode = CreateLTNode(x);
LTNode* posPrev = pos->prev;
posPrev->next = newnode;
newnode->prev = posPrev;
newnode->next = pos;
pos->prev = newnode;
}
[外链图片转存中…(img-lmvpdvKC-1712583804638)]
删除pos位置
void LTErase(LTNode* pos)
{
LTNode* posPrev = pos->prev;
LTNode* posNext = pos->next;
posPrev->next = posNext;
posNext->prev = posPrev;
free(pos);
}
[外链图片转存中…(img-1UYS5e94-1712583804638)]
顺序表和链表的优势和问题
顺序表优势和问题
顺序表优势: (物理内存连续)
支持下标随机访间。O(1)读取数据的时候内存污染低
顺序表问题:
1、头部或者中间插入删除效率低,要挪动数据。O(N)
2、空间不够需要扩容,扩容有一定的消耗,且可能存在一定的空间浪费
3、只适合尾插尾删
链表优势和问题
链表(双向)优势:
1、任意位置插入删除都是O(1)
2、按需申请释放,合理利用空间,不存在浪费
问题:
1、下标随机访问不方便 O(N))读取数据的时候内存污染高