1 review of class on nov 30:. 2 chapter 12: structures and adts outline declaring structures ...

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Review of Class on Nov 30:

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Chapter 12: Structures and ADTs

Outline Declaring Structures Accessing a Member in a structure variable Initialization of Structures Self-Referential Structures Linear Linked Lists The use of typedef

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Self-Referential Structures

self-referential structures structures with pointer members that point

to the structure type containing them. Example:

struct list{ int data; struct list *pNext; } a, b, c;

member pNext points to the structure type struct list, which contains pNext as a member

struct list is a self-referential structure.

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Self-Referential Structures

Using self-referential structures to implement linear linked lists

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&b

a

2

&c

b

3

NULL

c

struct list{ int data; struct list *pNext; } a, b, c; a.data=1; b.data=2; c.data=3; a.pNext = &b; b.pNext = &c; c.pNext = NULL;

data

pNext

data

pNext

data

pNext

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Linear Linked Lists

What is linear Linked List?How to implement linear linked lists

create a list counting and lookup insertion deletion

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Linear Linked Lists

What is Linear Linked List? a list on which data structures hang

sequentially.a head pointer that points to the first

element of the list, each element points at a successor

element,the last element having a link value

NULL.

pHead

struct list{ int data; struct list *pNext; } a, b, c;

1

&b

2

&c

3

NULL

data

pNext

data

pNext

data

pNext

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Linear Linked Lists

Linear Linked Lists A linked list is a very common data

structure. It can be used to implement efficient

algorithms, such as sorting, searching.

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Linear Linked Lists

What is linear Linked List?How to implement linear linked lists

create a list counting and lookup insertion deletion

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Linear Linked Lists

How to implement linear linked lists Consider the following list:

struct linked_list{ char data; struct linked_list *pNext;};

pHead

data

data

data

data

data

data …………

NULL

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Linear Linked Lists

Operations on a linked listDefine functions such that create a list

from a value of type charfrom an array of type char

counting: the number of elements looking up an element inserting an element deleting an element


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Linear Linked Lists

Operations on a linked list create a list from a value:

struct linked_list *create_value(char d);create a list that contains a single item;the value of member data in this item is equal to

dthe head pointer of this list is returned.

struct linked_list * pHead;pHead = create_value(‘A’);

pHead

‘A’

NULL


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#include <stdio.h>struct linked_list{ char data; struct linked_list *pNext;};struct linked_list *create_value(char data);#include "list.h"int main(){ struct linked_list *pHead; pHead = create_value('A'); …….}

list.h

main.c

#include "list.h"struct linked_list *create_value(char data){ struct linked_list *pHead = NULL; pHead = (struct linked_list *) malloc(sizeof(struct linked_list)); pHead->data = data; pHead->pNext = NULL; return pHead;}

list.c

pHead

‘A’

NULL

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Linear Linked Lists

Operations on a linked list create a linked list from an array:

struct linked_list *create_array(char data_array[], int n);

a list that contains n items is created.the member data of each item is set according to

data_array.the head pointer of this list is returned.

char data_array[]={'a', 'b', 'c', 'd', 'e'};struct linked_list * pHead;

pHead = create_array(data_array, 5);

pHead

‘a’ ‘b’ ‘c’ ‘d’ ‘e’

NULL


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#include <stdio.h>struct linked_list{ char data; struct linked_list *pNext;};struct linked_list *create_array(char data_array[],

int n);

#include "list.h"int main(){ struct linked_list *pHead; char data_array[]={'a', 'b', 'c', 'd', 'e'}; pHead = create_array(data_array, 5); ……}struct linked_list *create_array(char data_array[], int n){

struct linked_list *p=NULL, *pHead = NULL; int i; if(n==0) return NULL; else{ pHead = (struct linked_list *) malloc(sizeof(struct linked_list)); pHead->data = data_array[0]; pHead->pNext = NULL; p = pHead; for (i=1; i<n;i++){ p->pNext = (struct linked_list *) malloc(sizeof(struct linked_list)); p->pNext->data = data_array[i]; p->pNext->pNext = NULL; p = p->pNext; } } return pHead;}

list.h main.c

pHead

‘a’ ‘b’ ‘c’ ‘d’ ‘e’NULL

list.c

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Linear Linked Lists

Operations on a linked list count the elements in a list

int count(struct linked_list *pHead);Given a list, the head of which is pointed at by

pHead, the number of elements in this list is returned.

The value of count(pHead) is equal to 5

pHead

‘a’ ‘b’ ‘c’ ‘d’ ‘e’

NULL


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int count(struct linked_list *pHead){ int i=0; while(pHead!=NULL){ pHead = pHead->pNext; i++; } return i;}

#include <stdio.h>struct linked_list{ char data; struct linked_list *pNext;};struct linked_list *create_array(char data_array[], int n);int count(struct linked_list *pHead);

#include "list.h"int main(){ struct linked_list *pHead; char data_array[]={'a', 'b', 'c', 'd', 'e'}; pHead = create_array(data_array, 5); printf("%d", count(pHead));}

list.h

list.c

main.c

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Linear Linked Lists

Operations on a linked list Search a list for a particular element.struct linked_list* lookup(char data, struct linked_list *pHead);

If the element is found, a pointer to that element is returned; otherwise the NULL pointer is returned.

The value of lookup(‘b’, pHead) is a pointer pointing to the second elements

pHead

‘a’ ‘b’ ‘c’ ‘d’ ‘e’

NULL


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#include <stdio.h>struct linked_list{ char data; struct linked_list *pNext;};struct linked_list *create_array(char data_array[], int n);struct linked_list* lookup(char data, struct linked_list *pHead);struct linked_list* lookup(char data, struct linked_list *pHead){ while(pHead!=NULL){ if (pHead->data == data) return pHead; pHead = pHead->pNext; } return pHead;}

#include "list.h"int main(){ struct linked_list *pHead; struct linked_list *p; char data_array[]={'a', 'b', 'c', 'd', 'e'}; pHead = create_array(data_array, 5); p = lookup(‘c', pHead); if (p!=NULL) printf("Look UP: ‘c' is found \n"); else printf("Look UP: ‘c' is not found \n");}

list.h

main.c

list.c

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Linear Linked Lists

Operations on a linked list inserting an element

void insert(struct linked_list *p, char d);

Insert the data after the element pointed at by pBefore

After insert(p, ‘A’);

pHead

‘a’ ‘b’ ‘c’ ‘d’ ‘e’NUL

Lp

pHead

‘a’ ‘b’ ‘c’ ‘d’ ‘e’NUL

Lp

‘A’


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#include <stdio.h>struct linked_list{ char data; struct linked_list *pNext;};struct linked_list *create_array(char data_array[], int n);void insert(struct linked_list *p, char data);

void insert(struct linked_list *p, char data){/*Insert the data after the element pointed at by p*/

struct linked_list *pData; pData = (struct linked_list *) malloc(sizeof(struct linked_list)); pData -> data = data; pData->pNext = p->pNext; p->pNext = pData;}

#include "list.h"int main(){ struct linked_list *pHead = NULL; struct linked_list *p; char data_array[]={'a', 'b', 'c', 'd', 'e'}; pHead = create_array(data_array, 5); insert(pHead, 'A'); ………}

list.c

main.c

list.h

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Linear Linked Lists

Operations on a linked list Deleting an element

void delete (struct linked_list *p);

delete the element pointed at by p->pNext.Before

After delete(p)

pHead

‘a’ ‘b’ ‘c’ ‘d’ ‘e’NUL

Lp

pHead

‘a’ ‘b’ ‘c’ ‘e’NUL

Lp


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#include <stdio.h>struct linked_list{ char data; struct linked_list *pNext;};struct linked_list *create_array(char data_array[], int n);void delete(struct linked_list *p);

void delete(struct linked_list *p){ /* delete the element pointed at by p->pNext. */ struct linked_list *q; q = p->pNext; p -> pNext = q -> pNext;}

#include "list.h"int main(){ struct linked_list *pHead; struct linked_list *p; char data_array[]={'a', 'b', 'c', 'd', 'e'}; pHead = create_array(data_array, 5); delete(pHead->pNext); delete(pHead); …………}

main.c

list.c

list.h

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Linear Linked Lists

Operations on a linked list Release memory allocated to the list Dynamic Memory Allocation: space allocated

by calloc() and malloc() remains in use for the duration of the program unless it is released by the programmer.void release_list(struct linked_list *pHead)

o release the space allocated to the elements in the list.


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#include <stdio.h>struct linked_list{ char data; struct linked_list *pNext;};struct linked_list *create_array(char data_array[], int n);void release_list(struct linked_list *pHead);

void release_list(struct linked_list *pHead){ struct linked_list *p; while (pHead !=NULL){ p = pHead; pHead = pHead->pNext; p -> pNext = NULL; free(p); }}

#include "list.h"int main(){ struct linked_list *pHead; struct linked_list *p; char data_array[]={'a', 'b', 'c', 'd', 'e'}; pHead = create_array(data_array, 5); ………… release_list(pHead); …………}

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Linear Linked Lists

Summary What is linear Linked List How to implement linear linked lists

create a linked listcounting and lookupinsertion and deletion


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The Use of typedef

typedef an identifier can be associated with a specific type Example:

typedef char DATA;DATA a, b, c; /* char a,b,c; */

struct linked_list{ char data; struct linked_list *pNext;

};typedef struct linked_list ELEMENT;typedef ELEMENT * LINK;LINK pHead;

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1 review of class on nov 30:. 2 chapter 12: structures and adts outline declaring structures ...

Documents

list pheaddata

following list

data pheadpnext

data structures

linear linked lists

phead data null slide

phead phead

int data