A.5. Chapter 5: Branching A.5.1. Quiz -
Solution to Question 51 .
-
if , else , switch . -
Solution to Question 52 .
-
False. In C#, an if statement's condition must evaluate to a Boolean expression. -
Solution to Question 53 .
-
The braces make maintenance easier. If you add a second statement later, you are less likely to create a logic error because it is obvious what "block" of statements the if refers to. -
Solution to Question 54 .
-
Either a numeric value or a string. -
Solution to Question 55 .
-
False. If the statement has no body, then you can fall through. For example: case morning: case afternoon: someAction( ); break;
-
Solution to Question 56 .
-
Two uses of goto are: -
Solution to Question 57 .
-
do...while evaluates its condition is at the end of the statement rather than at the beginning, and thus is guaranteed to run at least once. -
Solution to Question 58 .
-
In a loop, it causes the remainder of the body of the loop to be skipped and the next iteration of the loop to begin immediately. -
Solution to Question 59 .
-
Two ways of creating an infinite loop are: for (;;) while(true)
A.5.2. Exercises -
Solution to Exercise 5-1 .
-
Create a method that counts from 1-10 using each of the while , do...while , and for statements. using System; class Exercises { static void Main( ) { Console.WriteLine( "while" ); int counter = 1; while ( counter <= 10 ) { Console.Write( counter ); if ( counter < 10 ) { Console.Write( ", " ); } ++counter; } Console.WriteLine( "\nDo..while" ); counter = 1; do { Console.Write( counter ); if ( counter < 10 ) { Console.Write( ", " ); } ++counter; } while ( counter <= 10 ); Console.WriteLine( "\nfor" ); for ( int ctr = 1; ctr <= 10; ctr++ ) { Console.Write( counter ); if ( counter < 10 ) { Console.Write( ", " ); } } Console.WriteLine( "\nDone" ); } }
-
Solution to Exercise 5-2 .
-
Create a program that evaluates whether a given input is odd or even, a multiple of 10, or too large (over 100) by using four levels of if statement. Then expand the program to do the same work with a switch statement. using System; class Exercises { enum numericCondition { even, multiple, odd, tooBig, unknown, zero, }; static void Main() { // possible input conditions while ( true ) { // entering any symbol except a number will throw an exception // -- no error handling in this simple example Console.Write( "Enter a number please: " ); string theEntry = Console.ReadLine(); int theNumber = Convert.ToInt32(theEntry) ; Console.Write( "NestedIf {0}: ", theNumber ); // Logic: if the number is greater than 100, say it is too big // if it is even but not a multiple of 10 say it is even // if it is a multiple of ten, say so // if it is not even, say it is odd if ( theNumber <= 100 ) { if ( theNumber % 2 == 0 ) { if ( theNumber == 0 ) { Console.WriteLine( "zero is not even or odd nor a multiple of 10" ); } else { if ( theNumber % 10 == 0 ) { Console.WriteLine( "You have picked a multiple of 10" ); } else { Console.WriteLine( "Your number is even" ); } // end else not a multiple of 10 } // end else not zero } // end if even else { Console.WriteLine( "What an odd number to enter" ); } } // end if not too big else { Console.WriteLine( "Your number is too big for me." ); } Console.Write( "SwitchMethod {0}: ", theNumber ); // same logic, different implementation // set the enumerated condition numericCondition condition = numericCondition.unknown; // initialize condition = ( theNumber % 2 == 0 ) ? numericCondition.even : numericCondition.odd; if ( theNumber % 10 == 0 ) condition = numericCondition.multiple; if ( theNumber == 0 ) condition = numericCondition.zero; if ( theNumber > 100 ) condition = numericCondition.tooBig; // switch on the condition and display the correct message switch ( condition ) { case numericCondition.even: Console.WriteLine( "Your number is even" ); break; case numericCondition.multiple: Console.WriteLine( "You have picked a multiple of 10" ); break; case numericCondition.odd: Console.WriteLine( "What an odd number to enter" ); break; case numericCondition.tooBig: Console.WriteLine( "Your number is too big for me." ); break; case numericCondition.zero: Console.WriteLine( "zero is not even or odd nor a multiple of 10" ); break; default: Console.WriteLine( "I'm sorry, I didn't understand that." ); break; } } } }
-
Solution to Exercise 5-3 .
-
Create a program that initializes a variable i at 0 and counts up, and initializes a second variable j at 25 and counts down. Use a for loop to increment i and decrement j simultaneously . When i is greater than j , end the loop and print out the message "Crossed over!". using System; class Exercises { static void Main( ) { int i = -1; int j = -1; for (i = 0, j = 25; i < j; ++i, --j ) { Console.WriteLine("i: {0}; j: {1}", i, j); } Console.WriteLine( "Crossed over! i: {0}; j: {1}", i, j ); } }
The output looks like this: i: 0; j: 25 i: 1; j: 24 i: 2; j: 23 i: 3; j: 22 i: 4; j: 21 i: 5; j: 20 i: 6; j: 19 i: 7; j: 18 i: 8; j: 17 i: 9; j: 16 i: 10; j: 15 i: 11; j: 14 i: 12; j: 13 Crossed over! i: 13; j: 12
|
