C programming and Data Structures...

Copyright 2000-2018 Networking Laboratory

C programming and

Data Structures Overview

T. H. Cormen, C. E. Leiserson and R. L. Rivest

Introduction to Algorithms, 3rd Edition, MIT Press, 2009

Sungkyunkwan University

Hyunseung Choo

[email protected]

mailto:[email protected]

Algorithms

Contents

Functions

Invocations Function

Function Definitions Return

statements

Function Prototypes

Call by value and call by

reference

Recursions

Recursive Call

Examples

Structures

Struct Declaration

Structure Tag

Compatible Structure

Memory Allocation

Accessing a Member

Pointers

Pointer Variable

Passing Pointers to Functions

Exercise Problem

Networking Laboratory 2/78

Algorithms

Functions


Algorithms

Invocations Function (1/3)

Function

C 프로그램은하나이상의 Function들로구성

모든 c-program은반드시한개의 main() Function을포함

반복되는 codes의경우 function으로정의하여필요시마다그

function을호출하여사용함으로서 simplicity의향상

Function의종류

Library functions : System이제공하는 Predefined-Functions

User-defined functions : Programmer에의해작성된 Functions

Function Invocation

Function의호출 : Function_name() 의형식으로사용.

Function의종료 : Function을 Call한곳으로제어권의이동


Algorithms



Algorithms

Function Definitions (1/2)

Function이호출되기전반드시해당 Function을다음형식

으로정의해야한다.


Algorithms

Function Definitions (2/2)

Parameter Type List

Function 호출시전달되는 arguments에대응되는순서와 data

types을지정

Function body내에서 identifier로사용될수있다

Return type

Function 종료될때 return statement에의해전달되는 value 의 type.

Default type : integer type으로, 생략시자동 integer로간주

void type : Return Value가없는경우 void로지정


Algorithms

The Return Statement

Function의실행종료, 호출한곳으로 control을이전하는

statement

생략시는 function body 끝의 ‘}’를만났을때자동 return

복수개의 return문사용가능

단, 하나의 Function에서두개의값을동시에 return할수없음


Algorithms

The Return Value


Algorithms

Function Prototypes (1/2)

Function 사용을위해호출전에반드시필요한 Function 선

언문

prototype이생략가능한경우

모든조건이 default인경우생략가능 : return value의 type과

argument의 type이 integer인경우생략가능

function이 main() function전에정의된경우

선언형식

return-type function_name (parameter type list);


Algorithms

Function Prototypes (2/2)

Argument와 parameter의 type이일치하지않는경우

function prototype에서지정된 type으로 convert됨.


Algorithms

Function Definition Order

한개의 file로작성된 program의일반적순서

1. #include, #define statements

2. Enumeration types and typedef

3. struct definition

4. Function Prototypes

5. main() Function

6 Function Definitions


Algorithms

main( )안에서의 Function Definition


Algorithms

Developing Large Program (1/2)

대규모 Program의경우, 여러 ~.h 파일과 ~.c파일로나누어

작성할수있다.

Team에의한작업분담이용이해진다.

프로그램이변경될때마다변경된 ~.c 파일만을 compile함

으로서시간절약가능


Algorithms

Developing Large Program (2/2)


Algorithms

Call by Value and Call by Reference

Call-by-Value

Function Invocation이일어나면, argument의 value를전달받기위

한 parameter를위해메모리영역이새로생기며 argument의값이

새영역에 copy된다.

Function Invocation의 parameter를 identifier로사용하여그값을

function내에서변경한경우에도다른 memory영역을사용함으로써

실제 argument의값은변경되지않는다

Call-by-Reference

Function Invocation이일어나면 argument의 address를전달한다.

실제값의 address를변경하기때문에그값을 function내에서변경

한경우실제 argument값이변경된다.


Algorithms

Example of Call by Value


Algorithms

Example of Call by Reference


Algorithms

Recursions


Algorithms

Recursive Call

어떤함수가자기자신을호출하는것


Algorithms

Factorial을구하는예제


Algorithms

Array의평균을구하는예제


Algorithms

Drawing Patterns on the Screen (1/2)

제곱근을구하는예제


Algorithms

Drawing Patterns on the Screen (2/2)

역순으로문자를출력하는예제

입력받은문장의문자들을역순으로출력한다.


Algorithms

Structures


Algorithms

Array와 structure의차이점

array

Array의모든 element는같은 type이여야한다.

Index를사용하여각 element를 access한다.

structure

다른 type의 element로구성될수있다있다.

각 element는 name을갖는다.

Name에의해각 element를 access한다.


Algorithms

Struct Declaration

Collection of members(/elements)


Algorithms

Structure Tag

정의되는특정 structure를지정하기위한 name

한번 structure tag인 part가정의되면, 이제 tag를사용하여

같은 structure type으로선언할수있다.


Algorithms

Structure Tag와변수동시선언

structure tag를이용하여선언된변수는같은 structure type


Algorithms

Compatible Structure (1/2)

같은 type의 structure variable이면서로 assign 가능

compatible types의조건

Structure 정의와동시에선언되는모든 variables

같은 type의 structure 즉같은 tag에의해선언된모든 variables


Algorithms

Compatible Structure (2/2)

compatible type이아닐경우 =, ==, != 불가능


Algorithms

Memory Allocation

Structure로선언된데이터 type은

각 member들이메모리내에

순차적으로할당된다.

part1의 base address가 200이고,

integer size가 4byte라가정하면,

오른쪽그림과같이메모리가할당됨


Algorithms

Accessing a Member (1/3)

struct member operator ‘.’

Structure의각 member를 access하기위해 ‘.’를사용한다.


Algorithms


member operation


Algorithms


structure pointer


Algorithms

Structures as Argument

call-by-value로 struct가 copy되어사용된다.


Algorithms

Struct Pointer사용 (1/2)

call-by-reference로 struct의 address를전달한다.


Algorithms

Struct Pointer사용 (2/2)


Algorithms

The Use of typedef (1/2)

data type의 name을재정의하기위해사용

readability의증가


Algorithms

The Use of typedef (2/2)

typedef를사용, struct type을새로운 type으로선언


Algorithms

Pointers


Algorithms

Pointer Variable

포인터변수는변수명은같으나변수선언을할때 * 연산자

를사용한다.

int *a; → int형포인터

포인터변수는타입에상관없이 4바이트다.


Algorithms

Passing Pointers to Functions (1/4)

포인터를 argument로하는함수예제


Algorithms




Algorithms


포인터를 argument로하는함수사용시유의점


Algorithms

Exercise Problem

pointer의주소할당문제


Algorithms

Approaches

pointer의예제


Copyright 2000-2018 Networking Laboratory

Data Structures Overview

Sungkyunkwan University

Hyunseung Choo

[email protected]

mailto:[email protected]

Algorithms

Contents

Arrays

Arrays

Representation of

Multidimensional Arrays

Stacks and Queues

Stack Abstract Data Type

Queue Abstract Data Type

Circular Queues

Lists

Singly Linked Lists

Doubly Linked Lists


Algorithms

Arrays


Algorithms

Arrays (1/2)

An array is a set of pairs, <index, value>, such that each

index that is defined has a value associated with it

A consecutive set of memory locations in C

Logical order is the same as physical order

int list[5], *plist[5];

/* arrays start at index 0 in C */

- integers: list[0],..., list[4]

- int ptrs: plist[0],..., plist[4]


Algorithms

Arrays (2/2)

Variable Memory Address

list[0] base address = a

list[1] a + sizeof(int)

list[2] a + 2·sizeof(int)



list[i] in C programs, C interprets it as a pointer to an integer whose

address is the one in the table above

int *list1;

pointer variable to an int

int list2[5];

five memory locations for holding integers are reserved


Algorithms

Representation of Multidimensional Arrays

Internal Representation of Multidimensional Arrays

How to state n-dimensional array into 1-dimensional array?

How to retrieve arbitrary element in a[upper0][upper1]···[uppern-1]

the number of elements in the array

n-1

P upperii=0

e.g.) a[10][10][10]

→ 10*10*10 = 1000 (units)


Algorithms

1-dimensional Array

Starting-address + offset-value

Assume a: starting-address

1-dimensional array a[u0]

a[0] : a

a[1] : a + 1

: :

a[u0-1] : a + (u0 - 1)

&a[i] = α + i


Algorithms

2-dimensional Array

2-dimensional array a[u0][u1]

a[i][j] = α + i·u1 + j

0 1 · · · u 1 - 1

0 a a + 1 a +(u 1-1)

1

·

·

·

u 0 - 1

?i

j


Algorithms

Stacks and Queues


Algorithms

Stack Abstract Data Type

ADT stack Last-In-First-Out (LIFO) Ordered list, insertions and deletions are made at one end called

the “top”

Given stack S = (a0, ···, an-1)

a0 : bottom element

an-1 : top element

ai : on top of element ai-1 (0<i<n)

Inserting and deleting elements in stack

topA

topB

A

topC

B

A

topD

C

B

A

topE

D

C

B

A

topD

C

B

A


Algorithms

Implementing a Stack

Using a one-dimensional array stack[MAX_STACK_SIZE]

#define MAX_STACK_SIZE 100

typedef struct {

int key;

} element;

element stack[MAX_STACK_SIZE];

int top = -1;

Structure element consists of only a key field, and we can add

fields to or modify to meet the requirements of the application


Algorithms

Push and Pop

Pushvoid push(int *ptop, element item) {

if (*ptop >= MAX_STACK_SIZE - 1) {

stack_full();

return;

}

stack[++*ptop] = item;

}

Pop

element pop(int *ptop) {

if (*ptop == -1)

return stack_empty();

return stack[(*ptop)--];

}

push(&top, item)

pop(&top, item)


Algorithms

ADT queue First-In-First-Out (FIFO)

Ordered list

All insertions are made at one end called “rear”

All deletions are made at the other end called “front”

Inserting and deleting elements in queue

Queue Abstract Data Type

rearA

rearB

A

rearC

B

A

rearD

C

B

A

rearD

C

B

front

frontfrontfrontfrontfront

& rear

A


Algorithms

Implementing a Queue

A one-dimensional array, and two variables: front and rear

#define MAX_QUEUE_SIZE 100

typedef struct {

int key;

/* other fields */

} element;

element queue[MAX_QUEUE_SIZE];

int rear = -1;

int front = -1;


Algorithms

Add and Delete

Add to a queue

void addq(int *prear, element item) {

if (*prear == MAX_QUEUE_SIZE - 1) {

queue_full();

return;

}

queue[++*prear] = item;

}

Delete from a queue

element deleteq(int *pfront, int rear) {

if (*pfront == rear)

return queue_empty();

return queue[++*front];

}

In deleteq()

rear is used

to check for

an empty

queue

addq(&rear, item)

deleteq(&front, rear)


Algorithms

Circular Queues (1/3)

More efficient queue representation

Regarding the array queue[MAX_QUEUE_SIZE] as circular

Initially front and rear to 0 rather than -1

The front index always points one position counterclockwise from

the first element in the queue

The rear index points to the current end of the queue


Algorithms


Empty queue

[1]

[2] [3]

[4]

[0] [5]

front = 0

rear = 0

[1]

[2] [3]

[4]

[0] [5]

front = 0

rear = 3

J3

J1

J2

Empty and nonempty circular queues


Algorithms


Full queue

[1]

[2] [3]

[4]

[0] [5]

front = 0

rear = 5

[1]

[2] [3]

[4]

[0] [5]

front = 4

rear = 3

J9

J7

J8

J1

J2 J3

J4

J5 J6 J5

Full circular queues


Algorithms

Implementing Insertions and Deletions

Use modulus operator

Circular rotation of the rear

*rear = (*rear + 1) % MAX_QUEUE_SIZE

Circular rotation of the front

*front = (*front + 1) % MAX_QUEUE_SIZE;


Algorithms

Add to a Circular Queue

Add an item

void addq(int front, int *rear, element item)

{

*rear = (*rear + 1) % MAX_QUEUE_SIZE;

if (front == *rear) {

queue_full(rear);

/* reset rear and print error */

return;

}

queue[*rear] = item;

}

rotate rear before we place the item in queue[rear]

addq(front, &rear, item)


Algorithms

Delete from a Circular Queue

Delete an item

element deleteq(int *front, int rear)

{

element item;

if (*front == rear)

return queue_empty();

/* queue_empty returns an error key */

*front = (*front + 1) % MAX_QUEUE_SIZE;

return queue[*front];

}

deleteq(&front, rear)


Algorithms

Lists


Algorithms

Singly Linked Lists

Compose of data part and link part

Link part contains address of the next element in a list

Non-sequential representations

Size of the list is not predefined

Dynamic storage allocation and deallocation

bat satcat vat NULL

ptr


Algorithms

Insertion of Singly Linked Lists

To insert the word mat between cat and sat

1) Get a currently unused node (paddr)

2) Set paddr’s data to mat

3) Set paddr’s link to point to the address found in the link of the node

cat

4) Set the link of the node cat to point to paddr

bat satcat vat NULL

ptr

mat


Algorithms

Deletion of Singly Linked Lists

To delete mat from the lists

1) Find the element that immediately precedes mat, which is cat

2) Set its link to point to mat’s link

- No data movement in insert and delete operation

bat satcat vat NULL

ptr

mat


Algorithms

Doubly Linked Lists (1/2)

Problems of singly linked lists

Move to only one way direction

Hard to find the previous node

Hard to delete the arbitrary node

Doubly linked circular lists

Doubly lists + circular lists

Allow two links

Two way direction


Algorithms

Doubly Linked Lists (2/2)

Doubly linked circular lists with head node

head node

llink item rlink


Algorithms

Insertion of Doubly Linked Lists

Insertion into doubly linked circular listsvoid dinsert(node_ptr node,node_ptr newnode) {

/* insert newnode to the right of node */

newnode->llink = node;

newnode->rlink = node->rlink;

node->rlink->llink = newnode;

node->rlink = newnode;

}

time: O(1)

1.

2.

3.

4.

dinsert(node, newnode)

newnode

node

341 2

node

newnode

1

23

4

newnode

node


Algorithms

Deletion of Doubly Linked Lists

Deletion from a doubly linked circular listsvoid ddelete(node_ptr node, node_ptr deleted) {

/* delete from the doubly linked list */

if (node == deleted)

printf(“Deletion of head node not permitted.\n”);

else {

deleted->llink->rlink = deleted->rlink;

deleted->rlink->llink = deleted->llink;

free(deleted);

} }

time: O(1)

node

deleted

node

ddelete(node, deleted)

deleted

node


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