Introduction to Computer Science, Winter Term Lab Exercise 6 Discussion:

Transcription

1 German University in Cairo Faculty of Media Engineering and Technology Prof. Dr. Slim Abdennadher Dr. Rimon Elias Introduction to Computer Science, Winter Term Lab Exercise 6 Discussion: Exercise 6-1 Conditional Program Write a java program that asks a user for their birth year encoded as two digits (like "62") and for the current year, also encoded as two digits (like "99"). The program is to correctly write out the users age in years. Year of Birth: 62 Current year: 99 Your age: another run of the algorithm Year of Birth: 62 Current year: 00 Your age: 38 Note that depending on the current year, different operations have to be performed. To simplify the program assume that if the user enters a current year or birth year from 0 until 10 then the year is supposed to be from 2000 until 2010, otherwise the current year or the birth year is a year from 1911 until public class Age System.out.println("Year of birth:"); int birthyear = sc.nextint(); System.out.println("Current year:"); int currentyear = sc.nextint(); if ((currentyear>=0) && (currentyear<=10)) currentyear = currentyear; currentyear = currentyear; 1

2 if ((birthyear>=0) && (birthyear<=10)) birthyear = birthyear; birthyear = birthyear; int age = currentyear - birthyear; System.out.println("Your Age:"); System.out.println(age); Exercise 6-2 The Rabbitiski sequence of numbers is formed by the following rule: Each number is equal to the product of the 2 previous numbers. Write an algorithm that given the first two numbers and the length of the sequence n prints the Rabbitiski sequence consisting of n numbers. Example: Enter first number: 4 Enter second number: 5 Enter the length of the series: 5 The series is: public class Rabbitiski System.out.println("Enter the first number:"); int firstnumber = sc.nextint(); System.out.println("Enter the second number:"); int secondnumber = sc.nextint(); System.out.println("Enter the length of the series:"); int length = sc.nextint(); System.out.println(firstNumber); System.out.println(secondNumber); int i = 2; int result = 0; while (i < length) result = firstnumber * secondnumber; System.out.println(result); firstnumber = secondnumber; 2

3 secondnumber = result; i = i + 1; Exercise 6-3 A perfect integer is a positive integer that is equal to the sum of all of its proper divisors. A proper divisor of an integer n is an integer between 1 (inclusive) and n (exclusive) that divides n with no remainder. For example, 6 is a perfect number because 6 = Write a Java program that decides whether an integer is a perfect number. public class PerfectInt System.out.println("Enter the number:"); int counter = 2; int sumoffactors = 1; while(counter < n) if(n % counter == 0) sumoffactors = sumoffactors + counter; counter = counter + 1; if(sumoffactors == n) System.out.println("The number is perfect"); System.out.println("The number is not perfect"); Exercise 6-4 Write a Java program that given an integer number determines whether the number is a prime number. A prime number is a number that can only be divided by itself and 1. For example, 11 is a prime number because it can be only divided by 1 and 11. However, 8 is not a prime number since it can be divided by 1, 2, 4 and 8. 3

4 public class Prime int number = sc.nextint(); boolean result = true; if (number == 1) result = true; if (number == 0) result = false; int i = 2; while (i < number) if(number % i == 0) result = false; i = i + 1; System.out.println(result); Exercise 6-5 Write a Java program that given a decimal number any base, converts the number to its equivalent in the given base. Your program should not consider bases greater that 9. public class DecimalConversion System.out.println("Enter the number you want to convert:"); System.out.println("Enter the base:"); int base = sc.nextint(); String result = ""; while(n > 0) 4

5 int rem = n % base; result = rem + result; n = n / base; System.out.println("The equivalent of " +n+ " in base " +base+ " is: " +result); Exercise 6-6 Write a Java program that given a number any base and its base, converts the number to its equivalent decimal number. Your program should not consdier bases greater that 9. public class BaseConversion System.out.println("Enter the number you want to convert:"); System.out.println("Enter the base:"); int base = sc.nextint(); double result = 0; int i = 0; while(n > 0) int x = n % 10; result = result + (x * Math.pow(base,i)); n = n / 10; i = i +1; System.out.println("The deciaml equivalent of " +n+ " is: " +result); 5