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Iteration (Loop) partI. Thanachat Thanomkulabut. Consider the following program!. How to write “Hello, Kitty” 2000 times?. using System; Namespace SimPleExample { class SimPleC { static void Main() { Console.WriteLine(”Hello, Kitty”); Console.WriteLine(”Hello, Kitty”);

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Iteration (Loop) partI

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Iteration loop parti

Iteration (Loop) partI

Thanachat Thanomkulabut


Consider the following program

Consider the following program!

How to write “Hello, Kitty” 2000 times?

using System;

Namespace SimPleExample {

class SimPleC {

static void Main() {

Console.WriteLine(”Hello, Kitty”);

Console.WriteLine(”Hello, Kitty”);

Console.WriteLine(”Hello, Kitty”);

Console.WriteLine(”Hello, Kitty”);

Console.WriteLine(”Hello, Kitty”);

Console.WriteLine(”Hello, Kitty”);

Console.WriteLine(”Hello, Kitty”);

}

}

}

#Hello, Kitty 7 times


Looping version

Looping Version

How to write “Hello, Kitty” 2000 times?

using System;

Namespace SimPleLoopExample {

class SimLoopPleC {

static void Main() {

int i;

i = 0;

while (i<7) {

Console.WriteLine(”Hello, Kitty”);

i++;

}

}

}

}

#Hello, Kitty 7 times


Looping or iteration in c

Iteration

(repeat)

Looping or Iteration in C#

while

do…while

foreach

for


Kinds of iteration statements

Kinds of Iteration statements


Outline

Outline

  • while statements

  • Loop controls

  • do...while


While statement

while statement

For Single Statement

while (condition)

statement;

while (condition) {

statement 1;

statement 2;

.

.

.

statement N;

}

FALSE

Condition

TRUE

Statement

For Multiple Statements


While example

while...example

1. initialize value

How this program works?

n

static void Main() {

intn = 0;

while (n < 3)

{

Console.WriteLine(”Current value of n: {0}”,n);

n++; }

}

3

1

2

0

3. condition

FALSE

TRUE

Monitor

2. runner

Current value of n: 0

Current value of n: 1

Current value of n: 2


While example1

while...example

Monitor

Current value of n: 0

Current value of n: 0

How this program works?

1. initialize value

Current value of n: 0

n

static void Main() {

intn = 0;

while (n < 3)

Console.WriteLine(”Current value of n:{0}”, n);

n++;

}

0

3. condition

TRUE

{

Infinite Loop

}

2. runner


While example2

while...example

Monitor

SUM

N

Please input N:

5

static void Main() {

int N, SUM;

SUM = 0;

N = 0;

while (N >= 0) {

Console.Write(”Please input N: ”);

N = int.Parse(Console.ReadLine());

if (N>=0)

SUM = SUM+N;

}

Console.WriteLine(“SUM = {0}”, SUM);

}

5

0

-1

3

0

5

8

Please input N:

3

Please input N:

-1

1. initialize value

TRUE

SUM = 8

FALSE

3. condition

FALSE

TRUE

2. runner


While example3

while...example

static void Main()

{

int n,x,fact;

 Console.Write(“Enter value of n : “);

n = int.Parse(Console.ReadLine());

fact = n;

x = n-1;

while (x >= 1)

{

fact = fact*x;

x = x-1;

}

Console.WriteLine(“{0}! = {1}”,n,fact);

}

n

x

fact

4

4

0

3

2

1

*3

*2

*1

Monitor

1. initialize value

Enter value of n :

4

FALSE

TRUE

3. finish condition

4! = 24

2. runner


Test i

Test I

  • Write a program which

  • Input : n (positive integer number)

  • Output : summation of 1+2+3+...+n


Test i1

Test I

static void Main()

{

}

int n

;

,x=1

;

,sum=0;

Console.Write(“Enter value of n : ”);

n = int.Parse(Console.ReadLine());

while(x<=n)

{

}

sum = sum+x;

x++;

Console.Write(“sum = {0}”,sum);


While statements

While Statements

  • Since the condition is checked before the execution of the loop body

  • While loop is also called a pre-conditional loop.

  • As long as the entry condition is still true, the while loop will be repeated

  • Zero loop will be executed if the entry condition is false at the beginning

  • while statements are conditional iteration statements which execute the loop body only if the entry condition is true


Outline1

Outline

  • while statements

  • Loop controls

  • do...while


Loop controls

Loop Controls


Counter controlled

N <= 5

N++;

Counter Controlled

Monitor

N

1

2

4

3

6

5

1

2

static void Main() {

int N;

N = 1;

while ( )

{

Console.WriteLine(”{0}”, N);

}

}

3

FALSE

4

TRUE

5

How to display even numbers 1 to J on screen?


Counter controlled1

N <= J

N%2==0

N++;

Counter Controlled

  • Display only even numbers between 1 to J

static void Main() {

int N, J;

J = int.Parse(Console.ReadLine());

N = 1;

while ( ) {

if ( )

Console.WriteLine(”{0}”, N);

}

}

2

4

6

8

.

.

.

How to display odd numbers between 1 to J on screen?


Loop controls1

Loop Controls


Sentinel controlled

Sentinel-Controlled

Monitor

SUM

N

Please input N:

5

static void Main() {

int N, SUM;

SUM = 0;

N = 0;

while (N >= 0) {

Console.Write(”Please input N: ”);

N = int.Parse(Console.ReadLine());

if (N>=0)

SUM = SUM+N;

}

Console.WriteLine(“SUM = {0}”, SUM);

}

0

5

0

5

3

-1

8

Please input N:

3

Please input N:

-1

TRUE

SUM = 8

FALSE

FALSE

TRUE


Outline2

Outline

  • while statements

  • Loop controls

  • do...while


Kinds of iteration statements1

Kinds of Iteration statements


Do while statement

Statement3

Statement2

Statement1

do...while statement

do{

statement1;

statement2;

statement3;

}while (condition);

true

condition

false


Do while example

do...while example

How this program works?

N

Monitor

0

1

2

3

0

static void Main() {

int N = 0;

do{

Console.WriteLine(N);

N++; }while (N < 3);

}

1

2

FALSE

TRUE


Do while example1

do...while example

Input your password :

Kaset

How this program works?

Input your password :

bkk

input

static void Main() {

string input; do{

Console.Write("Input your password:");

input = Console.ReadLine();

}while(input != "ABCD");

Console.WriteLine("Password Correct");}

Input your password :

ABCD

bkk

Kaset

ABCD

Password Correct

TRUE

FALSE


Do while example2

do...while example

How this partial code works?

Monitor

n

x

Input :

6

int n,x=1; Console.Write("Input:"); n = int.Parse(Console.ReadLine());

Console.WriteLine("Factor of {0} is",n);

do{

if(n%x==0)

Console.WriteLine(x);

x++;

}while(x<=n);

6

6

7

1

5

3

2

4

Factor of 6 is

1

2

3

FALSE

TRUE

6

TRUE

FALSE


Test ii

Test II

  • Write a program

  • Input : n (negative integer number)

  • Output : summation of (-1)+(-2)+(-3) +...+n


Test ii1

Test II

static void Main()

{

}

int n

;

,x=-1

;

,sum=0;

Console.Write(“Enter value of n : ”);

n = int.Parse(Console.ReadLine());

do{

}while(x>=n);

sum = sum+x;

x--;

Console.Write(“sum = {0}”,sum);


Do while statement1

Do..while Statement

  • The loop body of a do..while statement will be executed first before the exit condition is checked

  • Do..while loop is also called a post-conditional loop because the condition is checked after the loop body

  • Do..while statement is a conditional iteration statements

  • A do..while statement will be executed at least once


Do while vs while

Statement

Statement

Statement

Do..while vs. While

Do..while statement

While statement

false

condition

true

Statement

Statement

true

condition

Statement

false


While do while more example

while & do..while more example

  • This program will reverse integer input

  • Example

    • input : 1502

    • output : 2051

static void Main()

{int number, right_digit;

Console.Write("Enter your number : ");

number = int.Parse(Console.ReadLine());

Console.Write("Reverse number is: ");

while (number != 0)

{right_digit = number%10;

Console.Write("{0}",right_digit);

number = number/10;

}

}

TRUE

FALSE

number

right_digit

1

5

0

2

1

0

15

1502

150

Monitor

Reverse number is:

2051

2

205

20


While do while more example1

while & do..while more example

  • This program shows odd n numbers starting from 1

  • Example

    • input : 5

    • output : 1 3 5 7 9

static void Main()

{int n, count, k;

Console.Write ("Please enter number of odd numbers: ");

n = int.Parse(Console.ReadLine());

k = 1; count = 1;

do{

Console.Write("{0} ",k);

k = k+2;

count = count+1;

}while (count<=n);

}

n

k

count

TRUE

FALSE

5

5

9

3

11

1

7

2

1

4

5

6

3

Monitor

1

3

5

9

7


Any question

Any question?


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