第四章鏈結串列 linked list

朝陽科技大學資管系李麗華

第四章鏈結串列Linked List

Fools look to tomorrow, wise men use tonight.

--李麗華資料結構講義

練功前的沉思Q1: Remember the pointer in C?Q2: What is linked list?Q3: What is single linked list?Q4: What is circular linked list?Q4: How to implement linked list using

C? Q5: What is the difference between

linked list and array? ( 優缺點 )Q6: When do I apply linked list to

solve problems?Q7: Do you aware any problem for link

list?


Review of Pointer in C The pointer data type in C means the data

stores the address that this address points to other data with the same type).

EX: int i, *ptr, *p ; i=10 ; ptr = &i ; p= (int *) malloc(sizeof(int)) ; *p = 1024 ; printr(“i=%d, *ptr=%d, *p=%d ”, i, *ptr, *p) free(p); 將記憶體釋回

10i FFF0

FFF0ptr FFF2

address

?p FFF4

1024 832A

取得記憶體


What is linked list?Def: A link list is a dynamic allocating list in which data is stored in a node and pointer(s) is used to indicate the position of the list.

Characteristics:1. The list is a dynamically allocated structure.

2. The size of the storage do not need to be declared in advance. 3.Dynamically create/dispose the node when a node is inserted/deleted. 4.Insertion and deletion can be done without any order.

node

data ptr


The data structure of a nodeExample of a node declared in C: struct node { int data; <--資料型態可自訂 struct node *next; }

Initialize a linked list, i.e., head = tail = NULL; head -> link = NULL; tail -> link = NULL

head nextNULL NULL

若指標指向 NULL,有時亦可畫成 :

data next

放資料內容放指標

Create a node: x=(struct node *)malloc(sizeof(struct node)); 名稱自訂 ,例如可叫 head,tail,ptr,x,y,z,…


Single Linked List A single linked list is a dynamic allocated list

where nodes are linked by one way pointer. Insertion and deletion of a node can be done in

any position of a list.

Head

DOG CAT BIRD BAT APE

Tail


Insert a node to the sorted list (1)

1. Get the memory for the new node x=(struct node *)malloc(sizeof(struct node)); x = num; ( 設 x 內存放某一數值 num) x->next = NULL ;2. To insert a node in a sorted list, we search the list from “head” and find the right position. Three possible positions are considered.

(1) insert to the head (2) insert to the middle (3) insert to the tail

Insert to the head x->next = head ; head = x;

Head100 200 300 400

Tail10

x


Insert a node to the sorted list (2)

Insert to the tail tail->next = x ; tail = x;

Head

100 200 300 400 Tail

500xInsert to the middle cur = head; while(x->data > cur->data) { pre = cur ; cur = cur -> next; } x->next = cur; pre -> next = x;

Head

100 200 300 400

Tail

250

x

curpre


Delete a node from the sorted list (1)

1. Find the node in the list. Deletion should be taken care in three different positions.(1) Delete from head

(2) Delete from middle (3) Delete from tail2. When found the node, adjust the link and dispose the node.

Dispose a node p: free(p) ;

Delete from head: p = head ; head = head->next; free(p);

Delete from tail: p = head ; while(p->next != tail) p = p ->next; p ->next = NULL; free(tail) ; tail = p;


Delete a node from the sorted list (2)

Delete a node in the middle cur = head; while(cur->next != NULL) { pre = cur ; cur = cur -> next; if (x->data == cur->data) { pre->next = cur->next; free(cur); } }

令欲刪除 x->data=300

Head

100 200 300 500

Tail

400

pre cur


Join Two Lists

Join x & y list into Z:struct node *c;

if (x==NULL) z = y ; 當 x 的 list為空 else if (y==NULL) z = x ; 當 y 的 list為空 else { z = x ; c = x ; while(c->next!=NULL) c = c -> next; c -> next = y; }

x

100 200 300 500

y

100 200 300 500

z


Invert a List

Invert a list:

struct node *cur,*pre,*nex;

nex = head;cur = NULL;while(nex != NULL){ pre = cur; cur = nex; nex = nex -> next cur-> next = pre;}tail = head;head = cur;

Head Tail

100 200 300 500

nex

Head Tail

100 200 300 500

Head Tail

100 200 300 500

Head Tail

100 200 300 500

pre

HeadTail

100 200 300 500

cur

nex

pre

pre

pre

cur

cur

cur

nex

nex

nex


Circular ListDef: A circular list is a list with its tail points to the head.

Head 100 200 300 500Tail

Insert node x to headWhen list is empty head=x; tail=x; x->next = x;

Insert node x to headWhen list is not empty x->next = head; tail -> next = x; head=x;

head x tail head xtailhead


Circular List Operation

Insert node x to tail tail -> next = x; x->next = head; tail = x;

Delete node p from head p = head; head = head -> next; tail -> next = head; free(p);

Delete node p from tail p = head; while(p->next != tail) p= p-> next; p -> next = head; free(tail); tail = p;

Delete node p from middle 做法與一般串列相同請參考前面內容


Join Two Circular ListsJoin A & B circular listAtail -> next = Bhead;Btail -> next = Ahead;

Ahead100 200 300

Atail Bhead100 200 300

Btail

Ahead100 200 300

Atail Bhead100 200 300

Btail


Double Linked List The problem of single linked list is that the search can only

be done through one way pointer. The double linked list is a type of circular list in which each node contains two way pointers.

pre data next

放左指標放資料放右指標

Head Tail10 10 10 10

struct node { int data ; <--資料型態可自訂 struct node *pre ; struct node *next ;}


Double Linked List Operation(1)

Insert node x to headWhen double linked list is empty head=x; tail=x; x->next = x;

Insert node x to headWhen double linked list is not empty x->next = head; tail -> next = x; head=x;

head x tail head xtailhead


Double Linked List Operation(2)

Insert node x to tail tail -> next = x; x->next = head; tail = x;

Delete node p from head p = head; head = head -> next; tail -> next = head; free(p);

Delete node p from tail p = head; while(p->next != tail) p= p-> next; p -> next = head; free(tail); tail = p;

Delete node p from middle 做法與一般串列相同請參考前面內容


Application—Stack & Queue


Polynomial Addition


大師—該動動腦囉 !! 第 1 題 , 第 3 題請寫出 double linked list 及 circular linked list 的反轉串

列之演算法 .

回家動動腦上課來發表你知道 Linked List 的問題嗎 ? -- 如果不小心沒有將 pointer 處理好 , 會產生哪些問題 ?? -- 如果忘了 free(ptr), 又會有什麼問題 ?? -- 如果指標指錯了 , 又可能產生哪些問題 ??


Worry is like a rocking chair--it will give you something to do but

it won’t get you anywhere.

煩惱好像讓你的腦袋有事做 ,

但卻無法幫助你解決事情

第四章 鏈結串列 linked list

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第四章鏈結串列 linked list