Linear table: a finite sequence of zero or more data elements
Emphasize a few points:
First it is a sequence. That is to say, there is an order between elements. If there are multiple elements, the first element has no predecessor, the last element has no successor, and the others have a predecessor and a successor.
Second, the linear table emphasis is limited.
The linear table has two physical structures, the first is a sequential storage structure, and the other is a chained storage structure.
The sequential storage structure of the linear table refers to storing the data elements of the linear table in sequence with a segment of storage units with consecutive addresses. The sequential storage structure is implemented with one-dimensional arrays in C language.
Advantages and disadvantages of linear table sequential storage structure
Advantages : Can quickly read elements at any position in the table
No need to add additional storage space to represent logical relationships between elements in the table
Disadvantage : Insert and delete operations require moving a lot of elements
When the linear table length varies greatly, it is difficult to determine the capacity of the storage space
"Broken" storage space
In fact, the biggest disadvantage of the sequential storage structure is that a large number of elements need to be moved during insertion and deletion, which obviously takes time. So we ushered in the second storage structure of linear table: chain storage structure
The characteristic of the chain storage structure is to use a group of arbitrary storage units to store the data elements of the linear table, and this group of storage units can be continuous or discontinuous.
In the sequential storage structure, each data element needs to store the data element information. Now in the chain structure, in addition to storing the data element information, the address of its successor element is also stored.
The field that stores data element information is called the data field, and the field that stores the immediate successor position is called the pointer field
Let's talk about the advantages of linked lists
struct pointer
Storage can be allocated dynamically
All nodes are discretely distributed, linked only by pointers
Ready to work
head File
#include "stdio.h"
#include "stdlib.h"
#include "math.h"
#include "time.h"
Macro definition and use of typedef
#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
#define MAXSIZE 20 /* 存储空间初始分配量 */
typedef int Status;/* Status是函数的类型,其值是函数结果状态代码，如OK等 */
typedef int ElemType;/* ElemType类型根据实际情况而定，这里假设为int */
Structure and its definition
typedef struct Node
{
ElemType data;
struct Node* next;
}Node;
typedef struct Node* LinkList; /* 定义LinkList */malloc function
Here is a brief introduction to the usage of malloc function
pointer itself = (pointer type *) malloc(sizeof(pointer type))
Note:
1. malloc returns an untyped pointer, which must be cast to the desired type when using it
2. After opening up the space, be sure to release the space, otherwise it will cause memory leaks.
3. The free(p) function releases the storage space of the variable pointed to by p and completely deletes a variable
Other considerations
When you pass a parameter to a function, whether or not the parameter is changed within the function determines what parameter form is used
If it needs to be changed, you need to pass a pointer to this parameter
If it does not need to be changed, this parameter can be passed directly.
Please always pay attention to this point, don't always encounter functions that ask for pointers for a while, and get confused when they don't want pointers for a while, and don't understand.
Let's talk about the basic operation of singly linked list
Initialization of a singly linked list (the head node pointer field is set to empty)
/* 初始化链式线性表 */
Status InitList(LinkList* L)
{
*L = (LinkList)malloc(sizeof(Node)); /* 产生头结点,并使L指向此头结点 */
if (!(*L)) /* 存储分配失败 */
return ERROR;
(*L)->next = NULL; /* 指针域为空 */
return OK;
}Determine whether the linked list is empty (actually it is based on whether the head node is empty. Returns 1 for empty, returns 0 for non-empty)
/* 初始条件：链式线性表L已存在。操作结果：若L为空表，则返回TRUE，否则返回FALSE */
Status ListEmpty(LinkList L)
{
if (L->next)
return FALSE;
else
return TRUE;
Clear the linked list
/* 初始条件：链式线性表L已存在。操作结果：将L重置为空表 */
Status ClearList(LinkList *L)
{
LinkList p,q;
p=(*L)->next; /* p指向第一个结点 */
while(p) /* 没到表尾 */
{
q=p->next;
free(p);
p=q;
}
(*L)->next=NULL; /* 头结点指针域为空 */
return OK;
}
Find the length of the linked list
/* 初始条件：链式线性表L已存在。操作结果：返回L中数据元素个数 */
int ListLength(LinkList L)
{
int i = 0;
LinkList p = L->next; /* p指向第一个结点 */
while (p)
{
i++;
p = p->next;
}
return i;
}value
/* 初始条件：链式线性表L已存在，1≤i≤ListLength(L) */
/* 操作结果：用e返回L中第i个数据元素的值 */
Status GetElem(LinkList L,int i,ElemType *e)
{
int j;
LinkList p; /* 声明一结点p */
p = L->next; /* 让p指向链表L的第一个结点 */
j = 1; /* j为计数器 */
while (p && j<i) /* p不为空或者计数器j还没有等于i时，循环继续 */
{
p = p->next; /* 让p指向下一个结点 */
++j;
}
if ( !p || j>i )
return ERROR; /* 第i个元素不存在 */
*e = p->data; /* 取第i个元素的数据 */
return OK;
}Find by value
/* 初始条件：链式线性表L已存在 */
/* 操作结果：返回L中第1个与e满足关系的数据元素的位序。 */
/* 若这样的数据元素不存在，则返回值为0 */
int LocateElem(LinkList L,ElemType e)
{
int i=0;
LinkList p=L->next;
while(p)
{
i++;
if(p->data==e) /* 找到这样的数据元素 */
return i;
p=p->next;
}
return 0;
}insert
/* 初始条件：链式线性表L已存在,1≤i≤ListLength(L)， */
/* 操作结果：在L中第i个位置之前插入新的数据元素e，L的长度加1 */
Status ListInsert(LinkList *L,int i,ElemType e)
{
int j;
LinkList p,s;
p = *L;
j = 1;
while (p && j < i) /* 寻找第i个结点 */
{
p = p->next;
++j;
}
if (!p || j > i)
return ERROR; /* 第i个元素不存在 */
s = (LinkList)malloc(sizeof(Node)); /* 生成新结点(C语言标准函数) */
s->data = e;
s->next = p->next; /* 将p的后继结点赋值给s的后继 */
p->next = s; /* 将s赋值给p的后继 */
return OK;
}
delete
/* 初始条件：链式线性表L已存在，1≤i≤ListLength(L) */
/* 操作结果：删除L的第i个数据元素，并用e返回其值，L的长度减1 */
Status ListDelete(LinkList *L,int i,ElemType *e)
{
int j;
LinkList p,q;
p = *L;
j = 1;
while (p->next && j < i) /* 遍历寻找第i个元素 */
{
p = p->next;
++j;
}
if (!(p->next) || j > i)
return ERROR; /* 第i个元素不存在 */
q = p->next;
p->next = q->next; /* 将q的后继赋值给p的后继 */
*e = q->data; /* 将q结点中的数据给e */
free(q); /* 让系统回收此结点，释放内存 */
return OK;
}The establishment of singly linked list - head insertion method
/* 随机产生n个元素的值，建立带表头结点的单链线性表L（头插法） */
void CreateListHead(LinkList* L, int n)
{
LinkList p;
int i;
srand(time(0)); /* 初始化随机数种子 */
*L = (LinkList)malloc(sizeof(Node));
(*L)->next = NULL; /* 先建立一个带头结点的单链表 */
for (i = 0; i < n; i++)
{
p = (LinkList)malloc(sizeof(Node)); /* 生成新结点 */
p->data = rand() % 100 + 1; /* 随机生成100以内的数字 */
p->next = (*L)->next;
(*L)->next = p; /* 插入到表头 */
}
}
The establishment of singly linked list - tail insertion method
/* 随机产生n个元素的值，建立带表头结点的单链线性表L（尾插法） */
void CreateListTail(LinkList* L, int n)
{
LinkList p, r;
int i;
srand(time(0)); /* 初始化随机数种子 */
*L = (LinkList)malloc(sizeof(Node)); /* L为整个线性表 */
r = *L; /* r为指向尾部的结点 */
for (i = 0; i < n; i++)
{
p = (Node*)malloc(sizeof(Node)); /* 生成新结点 */
p->data = rand() % 100 + 1; /* 随机生成100以内的数字 */
r->next = p; /* 将表尾终端结点的指针指向新结点 */
r = p; /* 将当前的新结点定义为表尾终端结点 */
}
r->next = NULL; /* 表示当前链表结束 */
}
Note: Regarding the data of p->data, you can also change it to manual input instead of having it randomly generated
The important thing is to understand the algorithm idea of the head insertion method or the tail insertion method
output
/* 初始条件：链式线性表L已存在 */
/* 操作结果：依次对L的每个数据元素输出 */
Status ListTraverse(LinkList L)
{
LinkList p = L->next;
while (p)
{
visit(p->data);
p = p->next;
}
printf("\n");
return OK;
}Status visit(ElemType c)
{
printf("%d ", c);
return OK;
}main function
int main()
{
LinkList L;
ElemType e;
Status i;
int j, k;
i = InitList(&L);
printf("初始化L后：ListLength(L)=%d\n", ListLength(L));
for (j = 1; j <= 5; j++)
i = ListInsert(&L, 1, j);
printf("在L的表头依次插入1～5后：L.data=");
ListTraverse(L);
printf("ListLength(L)=%d \n", ListLength(L));
i = ListEmpty(L);
printf("L是否空：i=%d(1:是 0:否)\n", i);
i = ClearList(&L);
printf("清空L后：ListLength(L)=%d\n", ListLength(L));
i = ListEmpty(L);
printf("L是否空：i=%d(1:是 0:否)\n", i);
for (j = 1; j <= 10; j++)
ListInsert(&L, j, j);
printf("在L的表尾依次插入1～10后：L.data=");
ListTraverse(L);
printf("ListLength(L)=%d \n", ListLength(L));
ListInsert(&L, 1, 0);
printf("在L的表头插入0后：L.data=");
ListTraverse(L);
printf("ListLength(L)=%d \n", ListLength(L));
GetElem(L, 5, &e);
printf("第5个元素的值为：%d\n", e);
for (j = 3; j <= 4; j++)
{
k = LocateElem(L, j);
if (k)
printf("第%d个元素的值为%d\n", k, j);
else
printf("没有值为%d的元素\n", j);
}
k = ListLength(L); /* k为表长 */
for (j = k + 1; j >= k; j--)
{
i = ListDelete(&L, j, &e); /* 删除第j个数据 */
if (i == ERROR)
printf("删除第%d个数据失败\n", j);
else
printf("删除第%d个的元素值为：%d\n", j, e);
}
printf("依次输出L的元素：");
ListTraverse(L);
j = 5;
ListDelete(&L, j, &e); /* 删除第5个数据 */
printf("删除第%d个的元素值为：%d\n", j, e);
printf("依次输出L的元素：");
ListTraverse(L);
i = ClearList(&L);
printf("\n清空L后：ListLength(L)=%d\n", ListLength(L));
CreateListHead(&L, 20);
printf("整体创建L的元素(头插法)：");
ListTraverse(L);
i = ClearList(&L);
printf("\n删除L后：ListLength(L)=%d\n", ListLength(L));
CreateListTail(&L, 20);
printf("整体创建L的元素(尾插法)：");
ListTraverse(L);
return 0;
}
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