Week 4 Homework Solutions

WeekFourHW.java

import java.util.Scanner;

/**
 * This class contains the solutions to
 * the Week 4 homework exercises.
 */
public class WeekFourHW {

    public static void main(String[] args) {

        // -------- MANDATORY PROBLEMS --------

        /* Problem 1: Get Average Score
        Suppose the following int array called math_scores is defined that
        contains the scores of students on a math test:
         */

        int[] math_scores = new int[]{93, 85, 82, 89, 80, 82, 87, 94, 100};

        /* Your task: Using a for-each loop, create a Java program that calculates
        the sum of elements in the array. Then, using this sum and the length of
        the array, calculate the average score on the math test. Finally, print
        the average score.
         */

        int sum = 0;
        for (int num: math_scores) {
            sum = sum + num;
        }

        int num_scores = math_scores.length;
        int average = sum / num_scores;

        System.out.println("\nMandatory Problem 1\n"); // to separate problems
        System.out.println("\tAverage score: " + average);

        /* Problem 2: Doubling Numbers
        Suppose the following double array called numbers is defined that
        contains the following decimal numbers:
         */

        double[] numbers = new double[]{33.1, 57.2, 90.4, 78.6, 112.3, 160.5};

        /* Your task: Using a for loop, create a Java program that doubles all
        the numbers in the array. Then, print the array. Note that
        System.out.println(numbers); does not work for the second part!
         */

        System.out.println("\nMandatory Problem 2\n"); // to separate problems

        // doubling the numbers
        for (int i = 0; i < numbers.length; i++) {
            numbers[i] = numbers[i] * 2;
        }

        // printing the array
        System.out.print("\tNumbers: { ");
        for (int j = 0; j < numbers.length; j++) {

            if (j != numbers.length - 1)
                System.out.print(numbers[j] + ", ");
            else
                System.out.print(numbers[j]);

        }
        System.out.println(" }");

        // -------- OPTIONAL PROBLEMS --------

        /*
        Problem 1: Find the False
        Suppose the following boolean array called bool_list is defined that
        contains the following boolean values:
         */

        boolean[] bool_list = new boolean[]{true, false, true, true, true, false,
                                            false, true, true, true, true, false};

        /*
        Your task: Create a Java program to find all the locations in the array where
        there is a false value. If there is a false value, then print “There is a
        false value at ” + index;
         */

        System.out.println("\nOptional Problem 1\n"); // to separate problems

        for (int k = 0; k < bool_list.length; k++) {
            if (!bool_list[k]) { // bool_list[k] == false is also fine
                System.out.println("\tThere is a false value at " + k);
            }
        }

        /*
        Problem 2: Guess the Number

        Using a while loop, create a program that satisfies the following:
            - The computer has a number between 1 and 100
            - The user tries to guess it
            - The computer tells it to go higher or lower
            - The user will keep guessing while the guess is not equal to the correct number
            - If the user guesses the correct number,  you should print “Congratulations!
              You guessed the right number!” and then you should exit the loop.
         */

        System.out.println("\nOptional Problem 2\n"); // to separate problems

        Scanner userInput = new Scanner(System.in); // create a scanner object
        int guess = 0;
        int num = 45;

        while (guess != num) {

            System.out.print("\tGuess a number from 1 to 100: "); // ask user
            String input = userInput.nextLine(); // get and store user input in string
            guess = Integer.parseInt(input); // change string to int value

            if (guess > num)
                System.out.println("\t" + guess + " is too high! Go lower");
            else if (guess < num)
                System.out.println("\t" + guess + " is too low! Go higher");
            else
                System.out.println("\tCongratulations! You guessed the right number!");

        }

    }
}