Selection StatementThanachat Thanomkulabut

Outline2

Boolean expression ifif statement nested if nested if statement switch case switch case statement Flowchart

Boolean Expression

Operators Comparison

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

Boolean And &&&& Or |||| Not !!

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Boolean Expression

0 and 0 = 00 and 1 = 01 and 0 = 01 and 1 = 1

0 or 0 = 00 or 1 = 11 or 0 = 11 or 1 = 1

not 0 = 1not 1 = 0

Boolean Expression Example

From the equation: X2+9X+10 = 0 How can we check that value of X is the

answer for above equation?

Condition: Is value Y even 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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Boolean Expression

Example: Boolean Expressions

double x = 4.0; Expression Value

x < 5.0 ___________x > 5.0 ___________x <= 5.0 ___________5.0 == x ___________x != 5.0 ___________(3!=4)&&(7<5) ___________(4>4)||(5<=10) ___________

truefalsetruefalsetrue

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Boolean Expression

falsetrue

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Boolean expression ifif statement nested if nested if statement switch case switch case statement Flowchart

if statement

Execute the specific statement when the ”condition””condition” becomes truetrue

Syntax:

if if (condition)(condition)

statement; statement;

if if (condition) (condition) {{

statement1; statement1;

statement2; statement2;

}}if if (condition)(condition) {{

statement; statement;

}}

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if statement

truetrue

truetrue

if statement8

conditionFalse

True

Statement

if if (condition)(condition)

statement; statement;

if if (condition)(condition) {{

statement; statement;

}}

if statement

if statement9

condition

FalseTrue

Statement1

Statement2

if if (condition)(condition) {{

statement1; statement1;

statement2; statement2;

}}

if statement

if statement

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if statement example BMI (Body Mass Index)

BMI Weight Status

Below 18.5 Underweight

18.5 – 24.9 Normal

25.0 – 29.9 Overweight

30.0 and Above 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 statement

BMI Weight Status

Below 18.5 Underweight

18.5 – 24.9 Normal

25.0 – 29.9 Overweight

30.0 and Above 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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double BMI = W /(H*H);double BMI = W /(H*H);

if(BMI<18.5)if(BMI<18.5) Console.WriteLine(“Underweight”);Console.WriteLine(“Underweight”);

if(BMI>=18.5 && BMI<=24.9)if(BMI>=18.5 && BMI<=24.9) Console.WriteLine(“Normal”);Console.WriteLine(“Normal”);

if(BMI>=25.0 && BMI<=29.9)if(BMI>=25.0 && BMI<=29.9) Console.WriteLine(“Overweight”);Console.WriteLine(“Overweight”);

if statement example

if(BMI>=30.0)if(BMI>=30.0) Console.WriteLine(“Obese”);Console.WriteLine(“Obese”);

if statement

Test I

Selfish Ratio

Ratio Output

More than 1 You are selfish

1 You break even

Less than 1 You are giver

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Selfish Ratio =RecievingRecieving

GivingGiving

if…else… statement

If conditioncondition is truetrue execute statement1statement1 If conditioncondition is falsefalse execute statement2statement2 Syntax:if if (condition)(condition)

statement1; statement1; //true//true

elseelse

statement2; statement2; ////falsefalse

if if (condition)(condition)

statement1; statement1; //true//true

elseelse { {

statement2; statement2; ////falsefalse

statement3; statement3; ////falsefalse

}}

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if statement

if…else… statement14

conditionFalseTrue

Statement2Statement1

if if (condition)(condition)

statement1; statement1; //true//true

elseelse

statement2; statement2; ////falsefalse

if statement

if…else… statement15

if if (condition)(condition)

statement1; statement1; //true//true

elseelse { {

statement2; statement2; ////falsefalse

statement3; statement3; ////falsefalse

}}

conditionFalseTrue

Statement2

Statement1

Statement3

if statement

if…else… statement example

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Write the program which check input number. input : integer number output : message to inform that number is

odd or even.

Value in N Output

Even Number It’s even number.

Odd Number It’s odd number.

if statement

if…else… statement example

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Value in N OutputEven Number It’s even number.

Odd Number It’s odd number.

if statement

if(n%2 == 0)if(n%2 == 0)

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

elseelse

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

Test II18

Write the program which find the value of function input : number output :

f(x) x

x2+1 x<0

x+2 x≥0

if statement

Outline19

Boolean expression ifif statement nested if nested if statement switch case switch case statement FlowChart

Nested 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 Console.WriteLine(“N is zero number”);number”); elseelse Console.WriteLine(“N is positive Console.WriteLine(“N is positive number”); number”); }}else else Console.WriteLine(“N is negative Console.WriteLine(“N is negative number”);number”);

if#1if#1

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Nested if statement

if#2if#2

Nested if statement

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

if (N > 0) if (N > 0) Console.WriteLine(“N is positive Console.WriteLine(“N is positive number”); number”);

elseelse if (N==0)if (N==0) Console.WriteLine(“N is zero Console.WriteLine(“N is zero number”);number”); elseelse Console.WriteLine(“N is negative Console.WriteLine(“N is negative number”);number”);

if#1if#1if#2if#2

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Nested if statement

Nested 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 Console.WriteLine(“N is zero number”);number”); elseelse Console.WriteLine(“N is positive Console.WriteLine(“N is positive number”); number”); }}else else Console.WriteLine(“N is negative Console.WriteLine(“N is negative number”);number”);

-5

-5 >= 0 False

N is negative number

N

-5

0

0

0 >= 0 TrueTrue

N is zero number

3

3

3 >= 0

False

N is positive number

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Nested if statement

Nested if statement

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

if (N > 0) if (N > 0) Console.WriteLine(“N is positive Console.WriteLine(“N is positive number”); number”);

elseelse if (N==0)if (N==0) Console.WriteLine(“N is zero Console.WriteLine(“N is zero number”);number”); elseelse Console.WriteLine(“N is negative Console.WriteLine(“N is negative number”);number”);

N

-4

-4

-4 > 0 FalseFalse

FalseFalse

N is negative number

0

0

0 > 0

TrueTrue

N is zero number

3

3

3 > 0 TrueTrue

N is positive number

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Exercise 1: Separated IF (simple)

if (eaten==true) {Console.WriteLine(“ I’ve already eaten”);}else {Console.WriteLine(“ I’ve not eat yet”);}if (like_noodle==true) {Console.WriteLine(“I like noodle”);}else {Console.WriteLine(“I don’t like noodle”);}

1. Have you eaten lunch?2. Do you like noodle?

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if (like_noodle==true) {Console.WriteLine(“I like noodle”);}else { Console.WriteLine(“I don’t like noodle”); if (like_friedrice==true) {Console.WriteLine(“I like friedrice”);} else {Console.WriteLine(“I don’t like friedrice”);} }

1. Do you like noodle? 2. If you don’t like noodle, do you like fried rice?

Exercise 2: Related two IF (full version)25

if (like_noodle==true) {Console.WriteLine(“I like noodle”);}else if (like_friedrice==true) {Console.WriteLine(“I like friedrice”);}else {Console.WriteLine(“I don’t like friedrice”);}

1. Do you like noodle? 2. If you don’t like noodle, do you like fried rice?

Exercise 2: Related two IF (short version)26

if (like_noodle==true) {Console.WriteLine(“I like noodle”);

if (love_SenYai==true) {Console.WriteLine(“I love Sen-Yai”);}

else{Console.WriteLine(“I don’t love Sen-Yai”);}

}else if (like_friedrice==true) {Console.WriteLine(“I like fried rice”);}else {Console.WriteLine(“I don’t like fried rice”);}

1. Do you like noodle? 1.1 If you like noodle, do you love Sen-Yai? 1.2 If you don’t like noodle, do you like fried rice?

Exercise 3: Nested two IF (short version)27

Nested if statement example28

Write the program which show student’s grade input : score of student output :

Score Grade

80 – 100 A

70 – 79 B

60 – 69 C

50 – 59 D

0 – 49 F

Nested if statement

Test III29

Write the program which calculation value of following function input : value of x output : function value of x according

with ...

Nested if statement

f(x) =f(x) =2x+10, x ≤ 52x+10, x ≤ 5

xx22+10, 5 < x ≤ 20+10, 5 < x ≤ 20xx33+10, x > 20+10, x > 20

Outline30

Boolean expression ifif statement nested if nested if statement switch case switch case statement Flowchart

switch…case statement

For selecting a statement where its label corresponds to the value of the switch expression.

switch (<expression><expression>){ case <constant-expression> <constant-expression> : <statements>;<statements>; break;break;

[default: <statements>;<statements>; break;break;]}

<expression><expression> must be int, must be int, char, stringchar, string

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switch...case statement

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Example: switch-case (1)

int day_num;

day name

1 Sunday

2 Monday

3 Tuesday

4 Wednesday

5 Thursday

6 Friday

7 Saturday

int day_num;

Console.Write("Input the day"); day_num = int.Parse(Console.ReadLine());

switch(day_numday_num) {case 1:1: Console.Write ("Today is Sunday"); break;

case 2:2: Console.Write("Today is Monday"); break; : default :: Console.Write ("I don’t know"); break;}

<expression><expression>

<constant-expression><constant-expression>

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switch...case statement

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Test III33

Write the program which show numbers of day in each months input : Abbreviation of months output : numbers of day in each months

Input Output

Jan 31

Feb 28 or 29

Mar 31

Api 30

May 31

... ...

switch...case statement

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Example: switch-case (2)string month;

Console.Write("Input Month"); month = Console.ReadLine();

switch(monthmonth) {case “Jan”:“Jan”: case “Mar”:“Mar”: case “May”:“May”: Console.Write("This month has 31days"); break; case “Apr”:“Apr”: case “Jun”:“Jun”: Console.Write("This month has 30days"); break; default :: Console.Write (“Wrong Input"); break;}

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switch...case statement

Input Output

Jan 31

Feb 28 or 29

Mar 31

Api 30

May 31

... ...

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Example: switch-case (3)

char op;Console.Write("Select + - / * :");op=char.Parse(Console.ReadLine());

switch(op){ case '+': Console.Write("{0}+{1}={2}", x,y,x+y); break; case '-': Console.Write("{0}-{1}={2}", x,y,x-y); break; : default: Console.Write("Try again"); break;}

<expression><expression> must be must be int, char, stringint, char, string

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

switch(day_num ) { case 1: Console.Write ("Sunday"); break;

case 2: console.Write("Monday"); break; : default : Console.Write(“Try again"); break;}

<expression><expression>

int versionint versionchar versionchar version

<constant-expression><constant-expression>

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switch...case statement

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Example: switch-case (4)

string op;Console.Write("Select + - / * :");op=Console.ReadLine();

switch(op){ case “+”: Console.Write("{0}+{1}={2}", x,y,x+y); break; case “-”: Console.Write("{0}-{1}={2}", x,y,x-y); break; : default: Console.Write("Try again"); break;}

<expression><expression> must be must be int, char, stringint, char, string

string versionstring version

<expression><expression>

<constant-expression><constant-expression>

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switch...case statement

Convert switch-case to if else

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

switch (a) { case 1 : case 2 : Console.WriteLine("Hi"); break; case 3 : case 4 : Console.WriteLine("Hello"); break; default : Console.WriteLine("Bye"); break;}

switch version with defaultswitch version with default

if (a == 1 || a == 2) Console.WriteLine("Hi");

else if (a == 3 || a == 4) Console.WriteLine("Hello");

else Console.WriteLine("Bye");

if else versionif else version

switch (a) { case 1 : case 2 : Console.WriteLine("Hi"); break;}

switch version without defaultswitch version without default

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switch...case statement

Outline38

Boolean expression ifif statement nested if nested if statement switch case switch case statement Flowchart

Flowchart Symbols Overview

Graphical representation

Terminator

Process

Input/output

Condition

Connector

Flow line

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Flowchart

Program Flowchart Example

StartStart

Statement1Statement1

Statement2Statement2

Statement3Statement3

Statement4Statement4

EndEnd

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Flowchart

if statement flowchartstatement1;statement1;

if if (condition)(condition)

statement2; statement2; ////truetrue

elseelse { {

statement3; statement3; ////falsefalse

}}

statement4; statement4;

StartStart

Statement1Statement1

ConditionCondition

Statement2Statement2 Statement3Statement3

truetrue falsfalsee

Statement4Statement4

EndEnd

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Flowchart

if statement flowchart42n= n= int.Parse(Console.Reaint.Parse(Console.ReadLine());dLine());

if if (n>0)(n>0)

n= 2*n+5; n= 2*n+5;

elseelse { {

Console.Write(“Go”);Console.Write(“Go”);

n = n%4;n = n%4;

}}

StartStart

n>0n>0

n=2*n+5;n=2*n+5;

truetrue falsefalse

n=n%4;n=n%4;

EndEnd

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

Console.Write(“Go”);

Test IV43

Write flow chart which accord to following programn= n=

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

n = n%5;n = n%5;

if if (n==2)(n==2)

Console.WriteLine(“Remainder Console.WriteLine(“Remainder is 2”);is 2”);

elseelse { {

n = n*10;n = n*10;

}}

Console.WriteLine(“Program Console.WriteLine(“Program End”);End”);

Any question?