1. Iteration (Loop) partII
Thanachat Thanomkulabut

2. Switch-case example <expression> must be int, char, string
review 2
<expression> must be int, char, string
char version
int version
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); :
default:
Console.Write("Try again"); }
int day_num;
day_num=
int.Parse(Console.ReadLine());
switch(day_num ) {
case 1:
Console.Write ("Sunday");
break;
case 2:
console.Write("Monday"); :
default :
Console.Write(“Try again"); }
<expression>

3. Switch-case example (continue)
review
<expression> must be int, char, string
string version
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); :
default:
Console.Write("Try again"); }
<expression>

4. Flowchart of Switch-case (1/2)
review
int day_num;
day_num=
int.Parse(Console.ReadLine());
switch(day_num) {
case 1:
Console.Write ("Sunday");
break;
case 2:
console.Write("Monday"); :
default :
Console.Write(“Try again"); }
statement1
label
(day_num)
label=1
label=2
default
statement2
statement n
(day_num=3)
label=3
statement3 :
(day_num=2)
(day_num=1)

5. Flowchart of Switch-case (2/2)
review
Flowchart of Switch-case (2/2) 5
int month;
Console.Write("Input Month");
month = int.Parse(Console.ReadLine());
switch(month)
{case 1:
case 3:
case 5: :
Console.Write("This month = 31days");
break;
case 4:
case 6:
Console.Write(" This month = 30days");
default :
Console.Write ("Input again"); }
label
(month)
label=1,3,5,…
default :
statement1
(month=1,3,5,…)
label=4,6,…
Statement２
(month=4,6,…)
statement n

6. Outline For statements Nested loops Break statements
Continue statements

7. Looping or Iteration in C#
while
Iteration
(repeat)
foreach
do…while
for

8. Kinds of Iteration statements
Conditional iteration
while
do...while
Definite iteration
For

9. for statement For Single Statement For Multiple Statements
for ( [initializers]; [condition]; [runner] )
statement;
For Multiple Statements
for ( [initializers]; [condition]; [runner] ) {
statement-1;
statement-2; .
statement-N; }

10. for statement Example of for statement 1 2 3 4
START
END
condition
true
false
Statement
runner
initializers
for ( [initializers]; [condition]; [runner] )
statement;
Example of for statement
static void Main() {
int i;
for(i = 1; i <= 4; i++) Console.WriteLine(i); }
FALSE
TRUE
Output 1 2 i 3 2 5 4 1 3 4

11. for statement example static void Main() Output { int k; A A A A A 5
for (k = 0; k <= 4; k++)
Console.Write("A ");
Console.Write(k); }
Output
A A A A A 5

12. for statement example
Write the program to show even number 2,4,6,...,n
static void Main() {
int k,n;
Console.Write(“Input n :”);
n = int.Parse(Console.ReadLine());
for ( ; ; ) }
k = 1
k <= n
k++
if(k%2==0)
Console.WriteLine(k);

13. for statement example
Write the program to show even number 2,4,6,...,n
static void Main() {
int k,n;
Console.Write(“Input n :”);
n = int.Parse(Console.ReadLine());
for ( ; ; ) }
k = 2
k <= n
k = k+2
Console.WriteLine(k);

14. Test I : Find n factorial
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);

15. Test II : Problem #1: Find5 i2
= 1*1 + 2*2 + 3*3 + 4*4 + 5*5
static void Main() {
int N=0, SUM=0, i=0;
Console.Write(”Please input number: ”);
N = int.Parse(Console.ReadLine());
for ( ??? ; ??? ; ??? )
SUM = SUM + ??? ;
Console.WriteLine(”SUM = {0}”, SUM); }

16. Outline For statements Nested loops Break statements
Continue statements

17. Nested Loops : Example Nested for loops
Do not use the same runner variable in the outer loop and the inner loop
for (int outer = 1; outer <= 4; outer++) {
for (int inner = 1; inner <=3; inner++) {
Console.WriteLine("Outer = {1} & Inner = {0}" , inner ,outer); }

18. Nested Loops : Example Output Outer = 1 & Inner = 1
for (int outer = 1; outer <= 4; outer++) {
for (int inner = 1; inner <=3; inner++) {
Console.WriteLine("Outer = {1} & Inner = {0}" , inner ,outer); }
Outer = 1 & Inner = 2
Outer = 1 & Inner = 3
Outer = 2 & Inner = 1
Outer = 2 & Inner = 2
Outer = 2 & Inner = 3
Outer = 3 & Inner = 1
Outer = 3 & Inner = 2
Outer = 3 & Inner = 3
Outer = 4 & Inner = 1
Outer = 4 & Inner = 2
Outer = 4 & Inner = 3

19. Nested Loops : Example Nested while loops int outer = 1;
while (outer <= 4) {
int inner = 1 ;
while (inner <= 3) {
Console.WriteLine("Outer = {1} & Inner = {0}" , inner ,outer);
inner := inner +1; }
outer := outer +1;

20. Nested Loops : Example Nested do...while loops int outer = 1; do {
int inner = 1;
Console.WriteLine("Outer = {1} & Inner = {0}" , inner ,outer);
inner := inner +1
} while (inner < 6);
outer := outer + 1;
inner := 1
}while (outer < 5);

21. Test III : Nested Loops : Example
Write the program to Show output 1 12
123
1234
12345
int i,j;
for( ; ; ) {
for( , , ) { }

22. Break statement
The break statement terminates the closest enclosing loop or switch statement in which it appears

23. Break statement example
int i,j;
for(i=1;i<=10;i++) {
Console.WriteLine(i);
if(i==5) break; }
Console.Write(“final i = {0}”,i); i 4 2 1 5 3
Output 1 2 3 4 5
final i = 5

24. Continue Statement i sum 1 3 2 +1 +3 +5 +7 +9 Output final sum = 253 2 +1 +3 +5 +7 +9
final sum = 25
int i=0,sum=0;
do{
i++;
if(i%2==0)
continue;
sum = sum+i;
}while(i<10);
Console.WriteLine("final sum={0}",sum);

25. Continue statement example
int i=0,sum=0;
for(i=1;i<=10;i++ ) {
if(i%2==0)
continue;
sum = sum+i; }
Console.WriteLine("final sum={0}",sum);

26. Any question?