1. Iteration (Loop) part II
Thanachat Thanomkulabut

2. For statements Nested loops Break statements Continue statements
Outline
For statements
Nested loops
Break statements
Continue statements

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

4. Kinds of Iteration statements
กำหนด
จำนวนครั้งที่ทำซ้ำได้
Iteration
Conditional iteration
while
do...while
Definite iteration
For

5. 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; }

6. for statement Statement runner 1 initializers 1 2 3 2 condition 3
START 1
initializers 1 2 3 2
for ( [initializers]; [condition]; [runner] )
statement;
condition
false
true
Statement 3
runner
END

7. for statement i <= 4 Example of for statement i++ 1 2 3 4 i = 1
START
END
i <= 4
true
false
WriteLine(i)
i++
i = 1
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 5 4 3 1 2 4

8. For Loop vs While Loop static void Main() { int i=1; int i;
for(i=1; i<=4; i++) Console.WriteLine(i); }
int i=1;
while ( i<=4 ) {
Console.WriteLine(i);
i++; }

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

10. 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);

11. IMPROVE Write the program to show even number 2,4,6,...,n k=k+2
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);

12. x power n(คูณสะสม ) int i,n,x, product;
Console.Write( “Enter value of x : “ );
x = int.Parse( Console.ReadLine( ) );
Console.Write( “Enter value of n : “ );
n = int.Parse( Console.ReadLine( ) );
product = 1; i=0;
while (i < n) {
product = product *x;
i = i+1; }
Console.WriteLine(“{0} power {1}={2}”, x,n, product);
Product = 1
Product = 1*x
Product= (1*x)*x
Product= (1*x*x)*x

13. 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);

14. Test I : Problem #1: Find i2 5 i =1 static void Main() {
= 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); }

15. Outline For statements Nested loops Break statements
Continue statements

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

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 for (int outer = 1; outer <= 4; outer++) }
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 II : 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);
If a continue statement is not enclosed by a while, do, for, or foreach statement, a compile-time error occurs.
When program control reaches a continue statement, it transfers to the third section within the for loop parentheses (i++). Once this is complete, control transfers to the boolean expression for evaluation in the next iteration.

26. Any question?