12nd Semester 2005
Selection Selection StatementStatement
Computer and ProgrammingComputer and Programming
(204111)(204111)
2
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
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