iteration (loop) parti thanachat thanomkulabut. consider the following program! using system;...
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Iteration (Loop) partIThanachat Thanomkulabut
Consider the following program!
using System;using System;Namespace SimPleExample {Namespace SimPleExample { class SimPleC {class SimPleC { static void Main() {static void Main() {
Console.WriteLine(”Hello, Kitty”);Console.WriteLine(”Hello, Kitty”); Console.WriteLine(”Hello, Kitty”);Console.WriteLine(”Hello, Kitty”); Console.WriteLine(”Hello, Kitty”);Console.WriteLine(”Hello, Kitty”); Console.WriteLine(”Hello, Kitty”);Console.WriteLine(”Hello, Kitty”); Console.WriteLine(”Hello, Kitty”);Console.WriteLine(”Hello, Kitty”); Console.WriteLine(”Hello, Kitty”);Console.WriteLine(”Hello, Kitty”); Console.WriteLine(”Hello, Kitty”);Console.WriteLine(”Hello, Kitty”);
}} }}}}
#Hello, Kitty 7 times#Hello, Kitty 7 times
How to write “Hello, Kitty” 2000 times?How to write “Hello, Kitty” 2000 times?
2
Looping Version
using System;using System;Namespace SimPleLoopExample {Namespace SimPleLoopExample { class SimLoopPleC {class SimLoopPleC { static void Main() {static void Main() { int i;int i;
i = 0;i = 0; while (i<7) {while (i<7) { Console.WriteLine(”Hello, Kitty”);Console.WriteLine(”Hello, Kitty”); i++;i++; }}
}} }}}}
#Hello, Kitty 7 times#Hello, Kitty 7 times
How to write “Hello, Kitty” 2000 times?How to write “Hello, Kitty” 2000 times?
3
Looping or Iteration in C#
foreachforeach
whilewhile
forfor
do…whiledo…whileIterationIteration(repeat)
4
Kinds of Iteration statements5
Outline
while statements Loop controls do...while
6
while statement
while (while (conditioncondition)) statement;statement;
while (while (conditioncondition) {) { statement 1;statement 1; statement 2;statement 2; .. .. .. statement N;statement N;}}
For Multiple StatementsFor Multiple Statements
For Single StatementFor Single Statement
7
Condition
Statement
FALSE
TRUE
while...example
static void Main() {static void Main() { int n = 0;int n = 0; while (n < 3)while (n < 3) { { Console.WriteLine(”Console.WriteLine(”Current value of n: {0}”,n);”,n); n++;n++; } }
}}
n
0
TRUE
Current value of n: 0
Monitor
1
Current value of n: 1
2
Current value of n: 2
3
FALSE
8
How this program works?1. initialize value1. initialize value
2. runner2. runner
3. condition3. condition
while...example
static void Main() {static void Main() { int n = 0;int n = 0; while (n < 3)while (n < 3) Console.WriteLine(”Console.WriteLine(”Current value of n:{{0}”, n);0}”, n); n++;n++;
}}
n
0
TRUE
Current value of n: 0
Monitor
Current value of n: 0
Current value of n: 0
{{
}}Infinite Loop
9
How this program works?1. initialize value1. initialize value
3. condition3. condition
2. runner2. runner
while...example10
static void Main() {static void Main() { int N, SUM;int N, SUM; SUM = 0;SUM = 0; N = 0;N = 0;
while (N >= 0) {while (N >= 0) { Console.Write(”Please input N: ”);Console.Write(”Please input N: ”); N = int.Parse(Console.ReadLine());N = int.Parse(Console.ReadLine()); if (N>=0)if (N>=0) SUM = SUM+N;SUM = SUM+N; }}
Console.WriteLine(“SUM = {0}”, SUM);Console.WriteLine(“SUM = {0}”, SUM);}}
N
0
SUM
0
TRUE
Please input N: 5
Monitor
5
TRUE
5 Please input N: 33 8
Please input N: -1
-1
FALSE
FALSESUM = 8
1. initialize value1. initialize value
2. runner2. runner
3. condition3. condition
while...example11
static void Main(){
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);
}
n x fact
Enter value of n :
Monitor
4
4 43
TRUE
*32 *21 *10
FALSE
4! = 24
1. initialize value1. initialize value
2. runner2. runner
3. finish condition3. finish condition
Test I12
Write a program which Input : n (positive integer number) Output : summation of 1+2+3+...+n
Test I13
static void Main(){
}
Console.Write(“Enter value of n : ”);n = int.Parse(Console.ReadLine());
int n
;,x=1;,sum=0;
while(x<=n){
}
sum = sum+x;x++;
Console.Write(“sum = {0}”,sum);
While Statements14
Since the condition is checked before the execution of the loop body
While loop is also called a pre-conditional loop.
As long as the entry condition is still true, the while loop will be repeated
Zero loop will be executed if the entry condition is false at the beginning
while statements are conditional iteration statements which execute the loop body only if the entry condition is true
Outline
while statements Loop controls do...while
15
Loop Controls16
Counter Controlled17
static void Main() {static void Main() { int N;int N; N = 1;N = 1; while ( ) while ( ) {{ Console.WriteLine(”{0}”, N);Console.WriteLine(”{0}”, N);
}}}}
N <= 5N <= 5
N++;N++;
N
1
TRUE
1Monitor
2 23
3
4
4
5
5
6
FALSE
How to display even numbers 1 to J on screen?How to display even numbers 1 to J on screen?
Counter Controlled18
Display only even numbers between 1 to J
static void Main() {static void Main() { int N, J;int N, J; J = int.Parse(Console.ReadLine());J = int.Parse(Console.ReadLine()); N = 1;N = 1; while ( ) {while ( ) { if ( )if ( ) Console.WriteLine(”{0}”, N);Console.WriteLine(”{0}”, N);
}}}}
N <= JN <= J
N++;N++;
22446688
..
How to display odd numbers between 1 to J on screen?How to display odd numbers between 1 to J on screen?
N%2==0N%2==0 ....
Loop Controls19
Sentinel-Controlled20
static void Main() {static void Main() { int N, SUM;int N, SUM; SUM = 0;SUM = 0; N = 0;N = 0;
while (N >= 0) {while (N >= 0) { Console.Write(”Please input N: ”);Console.Write(”Please input N: ”); N = int.Parse(Console.ReadLine());N = int.Parse(Console.ReadLine()); if (N>=0)if (N>=0) SUM = SUM+N;SUM = SUM+N; }}
Console.WriteLine(“SUM = {0}”, SUM);Console.WriteLine(“SUM = {0}”, SUM);}}
N
0
SUM
0
TRUE
Please input N: 5
Monitor
5
TRUE
5 Please input N: 33 8
Please input N: -1
-1
FALSE
FALSESUM = 8
Outline
while statements Loop controls do...while
21
Kinds of Iteration statements22
do...while statement23
do{do{ statement1;statement1; statement2;statement2; statement3;statement3;}while (}while (conditioncondition););
conditiontrue
false
Statement3
Statement2
Statement1
do...while example24
static void Main() {static void Main() {
int N = 0;int N = 0;
do{ do{
Console.WriteLine(N);Console.WriteLine(N);
N++;N++;
}while (N < 3); }while (N < 3);
}}
How this program works? N
0 0Monitor
1
TRUE
12
2
3
FALSE
do...while example25
static void Main() {static void Main() {
string input;string input;
do{ do{
Console.Write("Input your Console.Write("Input your
password:");password:");
input = Console.ReadLine();input = Console.ReadLine();
}while(input != "ABCD");}while(input != "ABCD");
Console.WriteLine("Password Console.WriteLine("Password
Correct");Correct");
}}
How this program works?input
Input your password : Kaset
Kaset
TRUE
Input your password : bkk
bkkInput your password : ABCD
ABCD
FALSE
Password Correct
do...while example26
int n,x=1;int n,x=1;
Console.Write("Input:"); Console.Write("Input:");
n = int.Parse(Console.ReadLine()); n = int.Parse(Console.ReadLine());
Console.WriteLine("Factor of {0} Console.WriteLine("Factor of {0}
is",n);is",n);
do{do{
if(n%x==0)if(n%x==0)
Console.WriteLine(x);Console.WriteLine(x);
x++;x++;
}while(x<=n); }while(x<=n);
How this partial code works?
FALSETRUE
n x
1Input :
Monitor
6
Factor of 6 is6
TRUE
1
2
2
3
3
4
FALSE
56
6
7
Test II27
Write a program Input : n (negative integer number) Output : summation of (-1)+(-2)+(-3)
+...+n
Test II28
static void Main(){
}
Console.Write(“Enter value of n : ”);n = int.Parse(Console.ReadLine());
int n
;,x=-1
;,sum=0;
do{
}while(x>=n);
sum = sum+x;x--;
Console.Write(“sum = {0}”,sum);
Do..while Statement29
The loop body of a do..while statement will be executed first before the exit condition is checked
Do..while loop is also called a post-conditional loop because the condition is checked after the loop body
Do..while statement is a conditional iteration statements
A do..while statement will be executed at least once
30
Do..while vs. While
false
true
Statementcondition
true
false
Statement
Statement
Statement
Do..while statement While statement
Statement
Statement
condition
while & do..while more example31
static void Main(){ int number, right_digit; Console.Write("Enter your number : "); number = int.Parse(Console.ReadLine()); Console.Write("Reverse number is: "); while (number != 0) {
right_digit = number%10;Console.Write("{0}",right_digit);number = number/10;
} }
This program will reverse integer input
Example input : 1502 output : 2051
number right_digit
1502
FALSETRUE
215015 0510
Monitor2202052051
1
Reverse number is:
while & do..while more example32
This program shows odd n numbers starting from 1
Example input : 5 output :
1 3 5 7 9
static void Main(){ int n, count, k; Console.Write ("Please enter number of odd numbers: "); n = int.Parse(Console.ReadLine()); k = 1; count = 1; do{
Console.Write("{0} ",k);k = k+2;count = count+1;
}while (count<=n); }
k count
Monitor
1 1 TRUEFALSE3579
1
2
3
3
5
4
7
5
9
11 6
n
5
Any question?