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Published byJesse Washington Modified over 9 years ago
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Iteration (Loop) partI Thanachat Thanomkulabut
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Consider the following program! using System; Namespace SimPleExample { class SimPleC { class SimPleC { static void Main() { static void Main() { Console.WriteLine(”Hello, Kitty”); Console.WriteLine(”Hello, Kitty”); } }} #Hello, Kitty 7 times How to write “Hello, Kitty” 2000 times? 2
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Looping Version using System; 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 How to write “Hello, Kitty” 2000 times? 3
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Looping or Iteration in C# foreach while for do…while Iteration (repeat) 4
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Kinds of Iteration statements 5 Iteration Conditional iteration whiledo...while Definite iteration For
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Outline while statements Loop controls do...while 6
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while statement while (condition) statement; statement; while (condition) { statement 1; statement 1; statement 2; statement 2;... statement N; statement N;} For Multiple Statements For Single Statement 7 Condition Statement FALSE TRUE
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while...example static void Main() { int n = 0; int n = 0; while (n < 3) while (n < 3) { Console.WriteLine(””,n); Console.WriteLine(” Current value of n: {0} ”,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 value 2. runner 3. condition
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while...example static void Main() { int n = 0; int n = 0; while (n < 3) while (n < 3) Console.WriteLine(” { 0}”, n); Console.WriteLine(” Current value of n: { 0}”, n); n++; n++;} n 0 TRUE Current value of n: 0 Monitor Current value of n: 0 { } Infinite Loop 9 How this program works? 1. initialize value 3. condition 2. runner
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while...example 10 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: 3 38 FALSE SUM = 8 1. initialize value 2. runner 3. condition
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while...example 11 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); } nxfact Enter value of n : Monitor 4 4 4 3 TRUE *32*21*10 FALSE 4! = 24 1. initialize value 2. runner 3. finish condition
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Test I 12 Write a program which Input : n (positive integer number) Output : summation of 1+2+3+...+n
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Test I 13 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);
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While Statements 14 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
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Outline while statements Loop controls do...while 15
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Loop Controls 16 Loop Controls Counter Controlled Sentinel Controlled
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Counter Controlled 17 static void Main() { int N; int N; N = 1; N = 1; while ( ) while ( ) { Console.WriteLine(”{0}”, N); Console.WriteLine(”{0}”, N); }} N <= 5 N++; N 1 TRUE 1 Monitor 2 2 3 3 4 4 5 5 6 FALSE How to display even numbers 1 to J on screen?
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Counter Controlled 18 Display only even numbers between 1 to J 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 <= J N++; 2 4 6 8. How to display odd numbers between 1 to J on screen? N%2==0..
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Loop Controls 19 Loop Controls Counter Controlled Sentinel Controlled
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Sentinel-Controlled 20 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: 3 38 FALSE SUM = 8
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Outline while statements Loop controls do...while 21
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Kinds of Iteration statements 22 Iteration Conditional iteration whiledo...while Definite iteration For
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do...while statement 23 do{ statement1; statement1; statement2; statement2; statement3; statement3; }while (condition); condition true false Statement3 Statement2 Statement1
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do...while example 24 static void Main() { int N = 0; int N = 0; do{ do{ Console.WriteLine(N); Console.WriteLine(N); N++; }while (N < 3); N++; }while (N < 3);} How this program works? N 0 0 Monitor 1 TRUE 1 2 2 3 FALSE
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do...while example 25 static void Main() { string input; do{ string input; do{ Console.Write("Input your password:"); Console.Write("Input your password:"); input = Console.ReadLine(); input = Console.ReadLine(); }while(input != "ABCD"); }while(input != "ABCD"); Console.WriteLine("Password Correct"); } Console.WriteLine("Password Correct"); } How this program works? input Input your password : Kaset TRUE Input your password : bkk Input your password : ABCD FALSE Password Correct
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do...while example 26 int n,x=1; Console.Write("Input:"); n = int.Parse(Console.ReadLine()); int n,x=1; Console.Write("Input:"); n = int.Parse(Console.ReadLine()); Console.WriteLine("Factor of {0} is",n); Console.WriteLine("Factor of {0} 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? FALSE TRUE nx 1 Input : Monitor 6 Factor of 6 is 6 TRUE 1 2 2 3 3 4 FALSE 5 6 6 7
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Test II 27 Write a program Input : n (negative integer number) Output : summation of (-1)+(-2)+(-3) +...+n
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Test II 28 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);
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Do..while Statement 29 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
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30 Do..while vs. While false true Statement condition true false Statement Do..while statement While statement Statement condition
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while & do..while more example 31 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 FALSE TRUE 2 15015 051 0 Monitor 2 20 2052051 1 Reverse number is:
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while & do..while more example 32 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 TRUEFALSE 3579 1 2 3 3 5 4 7 5 9 11 6 n 5
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