12nd Semester 2005

Selection Selection StatementStatement

Computer and ProgrammingComputer and Programming

(204111)(204111)

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ReviewReview

Input StatementInput Statement

Numeric Type ConversionNumeric Type Conversion More Arithmetic ExpressionsMore Arithmetic Expressions

Modify-n-Assign; e.g. Modify-n-Assign; e.g. sum += x;sum += x; Increment & Decrement; Increment & Decrement; x++x++ and and x--x--

MathMath Class Class

string yourname;string yourname;yourname = yourname = System.Console.ReadLine()System.Console.ReadLine();;string yourname;string yourname;yourname = yourname = System.Console.ReadLine()System.Console.ReadLine();;

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Lab ReviewLab Review

StatementsStatements Input StatementInput Statement

Fahrenheit to Celsius Conversion Fahrenheit to Celsius Conversion

int value;string input;input = System.Console.ReadLine();value = int.Parse(input);

int value;string input;input = System.Console.ReadLine();value = int.Parse(input);

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Lab Review (Cont’)Lab Review (Cont’)using System;namespace C2F_DegreeConverter { class C2F_DegreeConverterClass { static void Main() { string input; float Ctemp, Ftemp; Console.Write("Please input farenheit: "); input = Console.ReadLine(); Ftemp = int.Parse(input); Ctemp = (Ftemp-32)*5/9; Console.WriteLine("{0} degrees in farenheit is" + "equivalent to {1} in celcius", Ftemp, Ctemp); } }}

using System;namespace C2F_DegreeConverter { class C2F_DegreeConverterClass { static void Main() { string input; float Ctemp, Ftemp; Console.Write("Please input farenheit: "); input = Console.ReadLine(); Ftemp = int.Parse(input); Ctemp = (Ftemp-32)*5/9; Console.WriteLine("{0} degrees in farenheit is" + "equivalent to {1} in celcius", Ftemp, Ctemp); } }}

Obtaining “F”

Converse string to intFormula!

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OutlineOutline Boolean expression (Boolean expression (นิ�พจนิ�ทางนิ�พจนิ�ทาง

ตรรกศาสตร�ตรรกศาสตร�)) ifif statement ( statement (คำ�าส��งเง��อนิไขคำ�าส��งเง��อนิไข)) nested ifnested if statement ( statement (คำ�าส��งเง��อนิไขคำ�าส��งเง��อนิไข

ซ้�อนิซ้�อนิ)) switch caseswitch case statement ( statement (คำ�าส��งทางคำ�าส��งทาง

เลื�อกเลื�อก))

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Selection: Why do we Selection: Why do we need it?need it?

Everything in life involves selectionEverything in life involves selection

HungryHungry Check MoneyCheck Money MKMK

SteakSteak

Bar MaiBar Mai

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Boolean ExpressionBoolean Expression OperatorsOperators

ComparisonComparison Equal Equal ==== Not equal Not equal !=!= Less Less << Greater Greater >> Less than or equal to Less than or equal to <=<= Greater than or equal to Greater than or equal to >=>=

BooleanBoolean And And &&&& - - Not Not !! Or Or ||||

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Boolean Expression Boolean Expression ExampleExample

From the equation: XFrom the equation: X22+9X+10 = 0+9X+10 = 0 How can we check that value of X is the How can we check that value of X is the

answer for above equation? answer for above equation?

Condition: Is the value Y an even Condition: Is the value Y an even number?number?

((X*X +9*X +10) == 0) //true if X is the //true if X is the answeranswer

(Y%2 == 0) //true if Y is even//true if Y is even

OROR

(Y%2 != 1) //true if Y is even//true if Y is even

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Example: Boolean Example: Boolean ExpressionsExpressions

double x = 4.0;double x = 4.0; Expression ValueExpression Valuex < 5.0 x < 5.0 ______________________x > 5.0 x > 5.0 ______________________x <= 5.0 x <= 5.0 ______________________5.0 == x 5.0 == x ______________________x != 5.0 x != 5.0 ______________________

truefalsetrue

false

true

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OutlineOutline Boolean expressionBoolean expression ifif statementstatement nested ifnested if statement statement switch caseswitch case statement statement

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if statementif statement Execute the specific statement Execute the specific statement

when the when the “condition”“condition” becomes becomes truetrue

Syntax:Syntax:if if (condition)(condition)

statement;statement; //true//true

if if (condition)(condition) {{

statement1; statement1; //true//true

statement2; statement2; //true//true

}}

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if statement exampleif statement example

BMI (Body Mass Index)BMI (Body Mass Index)

BMIBMI Weight StatusWeight Status

Below 18.5Below 18.5 UnderweightUnderweight

18.5 – 24.918.5 – 24.9 NormalNormal

25.0 – 29.925.0 – 29.9 OverweightOverweight

30.0 and Above30.0 and Above Obese (Extremely Fat)Obese (Extremely Fat)

BMI = Weight in KilogramsWeight in Kilograms

(Height in Meters) X (Height in Meters)(Height in Meters) X (Height in Meters)

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if…else… statementif…else… statement If If conditioncondition is is truetrue execute execute

statement1statement1 If If conditioncondition is is falsefalse execute execute

statement2statement2 Syntax:Syntax:

if if (condition)(condition)

statement1; statement1; //true//true

elseelse

statement2; statement2; //false//false

if if (condition)(condition)

statement1; statement1; //true//true

elseelse { {

statement2; statement2; //false//false

statement3; statement3; //false//false

}}

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if…else… statement if…else… statement exampleexample

QuestionQuestion Value in variable N is Odd or Even Value in variable N is Odd or Even

Number?Number?Value in NValue in N OutputOutputEven NumberEven Number It’s even number.It’s even number.

OddOdd NumberNumber It’s odd number.It’s odd number.if if (___________________)(___________________)

Console.WriteLine(“It’s even Console.WriteLine(“It’s even number.”);number.”);

elseelse

Console.WriteLine(“It’s odd Console.WriteLine(“It’s odd number.”);number.”);

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OutlineOutline Boolean expressionBoolean expression ifif statement statement nested ifnested if statement statement switch caseswitch case statement statement

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Nested IF OverviewNested IF Overviewif#1if#1

if#2if#2if#3if#3

if#1if#1

if#2if#2

if#3if#3

else#1else#1

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Nested if statementNested if statement

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

if (N >= 0) if (N >= 0) {{ if (N==0)if (N==0) Console.WriteLine(“N is zero number”);Console.WriteLine(“N is zero number”); elseelse Console.WriteLine(“N is positive number”); Console.WriteLine(“N is positive number”); }}else else Console.WriteLine(“N is negative number”);Console.WriteLine(“N is negative number”);

if#1if#1

if#2if#2

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Nested if statementNested if statement

f(x) =f(x) =

2x+10, x ≤ 52x+10, x ≤ 5

xx22+10, 5 < x ≤ 20+10, 5 < x ≤ 20

xx33+10, x > 20+10, x > 20

RangeRange Boolean ExpressionBoolean Expression

x ≤ 5x ≤ 5 (x <= 5)(x <= 5)

5 < x ≤ 205 < x ≤ 20 ((5 < x) && (x <= 20))((5 < x) && (x <= 20))

x > 20x > 20 (x > 20)(x > 20)

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Nested if statementNested if statement

f(x) =f(x) =2x+10, x ≤ 52x+10, x ≤ 5xx22+10, 5 < x ≤ 20+10, 5 < x ≤ 20xx33+10, x > 20+10, x > 20

double fx = 0;double fx = 0;double x = double.Parse(Console.ReadLine());double x = double.Parse(Console.ReadLine());

if ( )if ( ) fx = 2*x + 10;fx = 2*x + 10;else if ( )else if ( ) fx = x*x + 10;fx = x*x + 10; else else fx = x*x*x + 10;fx = x*x*x + 10;

Console.WriteLine(“f(x) = {0}”, fx);Console.WriteLine(“f(x) = {0}”, fx);

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OutlineOutline Boolean expressionBoolean expression ifif statement statement nested ifnested if statement statement switch caseswitch case statement statement

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switch…case statementswitch…case statement For selecting a statement where its For selecting a statement where its

label corresponds to the value of the label corresponds to the value of the switch switch expressionexpression..switch (<expression><expression>)

{ case <constant-<constant-expression>expression>: <statements>;<statements>; break;break; [default: <statements>;<statements>; break;break;]}<expression><expression> must be int, char, string must be int, char, string

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Exercise 1: switch-caseExercise 1: switch-caseint day_num;int day_num; string day_name;string day_name;

11 SunSun

22 MondayMonday

33 TuesdayTuesday

44 WednesdayWednesday

55 ThursdayThursday

66 FridayFriday

77 SaturdaySaturday

How to write ”How to write ”IF StatementIF Statement” and ”” and ”Switch-case statementSwitch-case statement”?”?

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Exercise 2Exercise 2

Ex1Ex1

Please input month: Please input month: 55

Your month has 31 Your month has 31 days.days.

Input: month number (0-12)

Output: #day in that month 

Ex2Ex2

Please input month: Please input month: 22

Your month has 28 Your month has 28 days.days.

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Exercise 3Exercise 3 Calculate payment for Air-time Calculate payment for Air-time

usageusage Operator: LEMONOperator: LEMON

Input: Input: Promotion Type & Usage timePromotion Type & Usage timeOutput: Output: Payment pricePayment price

Example 4Example 4ProgramProgram

Promotion TypePromotion Type

Usage timeUsage timePayment pricePayment price

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Flowchart Symbols Flowchart Symbols OverviewOverview

Graphical representationGraphical representation

Terminator

Process

Input/output

Condition

Connector

Flow line

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Program Flowchart Program Flowchart ExampleExample

START

statement1statement1

statement2statement2

statement3statement3

statement4statement4

END

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if statement flowchartif statement flowchart

START

statement1statement1

statement2statement2

statement3statement3

END

CONDITIONCONDITION

truetrue

falsefalse

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SummarySummary Boolean ExpressionBoolean Expression Selection StatementsSelection Statements

if...else... Statementif...else... Statement switch-case Statementswitch-case Statement

if…else…if…else…

Selection ProblemsSelection Problems

switchswitch

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QuizQuiz

1 .1 . จงเต�มคำ�าลืงในิช่�องว่�างจงเต�มคำ�าลืงในิช่�องว่�างusing System;namespace C2F_DegreeConverter { class C2F_DegreeConverterClass { static void Main() { string input; // declare a var as string for ReadLine() float Ctemp, Ftemp; // temp in Celsius & Fahrenheit Console.Write("Please input farenheit: "); // ……(1)…… input = Console.ReadLine(); // ……(2)…… Ftemp = int.Parse(input); // ……(3)…… Ctemp = (Ftemp-32)*5/9; // ……(4)…… Console.WriteLine("{0} degrees in farenheit is" + "equivalent to {1} in celcius", Ftemp, Ctemp); // ……(5)…… } }}

using System;namespace C2F_DegreeConverter { class C2F_DegreeConverterClass { static void Main() { string input; // declare a var as string for ReadLine() float Ctemp, Ftemp; // temp in Celsius & Fahrenheit Console.Write("Please input farenheit: "); // ……(1)…… input = Console.ReadLine(); // ……(2)…… Ftemp = int.Parse(input); // ……(3)…… Ctemp = (Ftemp-32)*5/9; // ……(4)…… Console.WriteLine("{0} degrees in farenheit is" + "equivalent to {1} in celcius", Ftemp, Ctemp); // ……(5)…… } }}

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2.2. จงเข ยนิโปรแกรมเพ��อท�าร�บคำ�าอ&ณหภู*ม�องศาจงเข ยนิโปรแกรมเพ��อท�าร�บคำ�าอ&ณหภู*ม�องศาเซ้ลืเซ้ ยสแลื�ว่ท�าการแปลืงให�เป+นิองศาเซ้ลืเซ้ ยสแลื�ว่ท�าการแปลืงให�เป+นิองศาฟาเรนิไฮท�โดยแสดงคำ�าออกท �หนิ�าจอฟาเรนิไฮท�โดยแสดงคำ�าออกท �หนิ�าจอ

โปรแกรมท �เข ยนิข/0นิคำว่รให�ลื�กษณะการใช่�งานิโปรแกรมท �เข ยนิข/0นิคำว่รให�ลื�กษณะการใช่�งานิออกหนิ�าจอด�งนิ 0ออกหนิ�าจอด�งนิ 0

C x 9 = (F – 32) x 5C x 9 = (F – 32) x 5

Please enter the temperature in Celsius: 3232 degrees in Celsius is equal to 95 degrees in Fahrenheit

Please enter the temperature in Celsius: 3232 degrees in Celsius is equal to 95 degrees in Fahrenheit