Flow of Control: Loops

Author: sharaf-qeshta

chapter_04/Exercise_04_01/Exercise_04_01.java

@@ -0,0 +1,47 @@
+package chapter_04;
+
+import java.util.Scanner;
+
+/**
+ * 1. Write a fragment of code that will read words from the keyboard until the
+ * word done is entered. For each word except done, report whether its first
+ * character is equal to its last character. For the required loop, use a
+ * a. while statement
+ * b. do-while statement
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_01
+{
+    public static void main(String[] args)
+    {
+        Scanner scanner = new Scanner(System.in);
+
+        System.out.print("Enter a word: ");
+        String word = scanner.next();
+        while (!word.equals("done"))
+        {
+            if (word.charAt(0) == word.charAt(word.length()-1))
+                System.out.println("the first and the last characters of " + word + " the same");
+            else
+                System.out.println("the first and the last characters of " + word + " is not the same");
+            System.out.print("Enter a word: ");
+            word = scanner.next();
+        }
+
+        System.out.print("Enter a word: ");
+        word = scanner.next();
+        do
+        {
+            if (word.charAt(0) == word.charAt(word.length()-1))
+                System.out.println("the first and the last characters of " + word + " the same");
+            else
+                System.out.println("the first and the last characters of " + word + " is not the same");
+
+            System.out.print("Enter a word: ");
+            word = scanner.next();
+        }
+        while (!word.equals("done"));
+    }
+}

chapter_04/Exercise_04_02/Exercise_04_02.java

@@ -0,0 +1,20 @@
+package chapter_04;
+
+/**
+ * 2. Develop an algorithm for computing the quarterly balance in an equity
+ * fund. You can make one switch (the increase or decrease in the rate of
+ * return according to the increase or decrease in the level of risk) in a quarter.
+ * Interest is added to the fund at the end of each quarter. The quarterly
+ * interest rate is the yearly percentage rate divided by 4.
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_02
+{
+    // divide the annual interest rate by 4 and store it in x
+    // x => annualInterestRate/4
+    // loop 4 times
+    // every time equity => equity + (equity * x) + (equity * changeRate)
+    // and print the current equity
+}

chapter_04/Exercise_04_03/Exercise_04_03.java

@@ -0,0 +1,25 @@
+package chapter_04;
+
+/**
+ * 3. Develop an algorithm for a simple game of guessing at a secret five-digit
+ * code. When the user enters a guess at the code, the program returns two
+ * values: the number of digits in the guess that are in the correct position
+ * and the sum of those digits. For example, if the secret code is 53840, and
+ * the user guesses 83241, the digits 3 and 4 are in the correct position. Thus,
+ * the program should respond with 2 and 7. Allow the user to guess a fixed
+ * number of times.
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_03
+{
+    // let numberOfGuesses => 3
+    // loop numberOfGuesses times
+    // every time read a guess from the keyboard guess => userGuess
+    // let rightPositions => 0 and sum => 0
+    // loop through the characters in the user guess
+    // if the character in the user guess match the character secret word at
+    // the same position then increment rightPositions by one and add the
+    // digit to sum
+}

chapter_04/Exercise_04_04/Exercise_04_04.java

@@ -0,0 +1,21 @@
+package chapter_04;
+
+/**
+ * 4. Write a fragment of code that will compute the product of the first n
+ * positive even integers. For example, if n is 6, you should compute 2 × 4 ×
+ * 6 × 8 × 10 × 12.
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_04
+{
+    public static void main(String[] args)
+    {
+        int n = 6, j = 0, product = 1;
+        for (int i = 2; j < n; i+=2, j++)
+            product *= i;
+
+        System.out.println(product);
+    }
+}

chapter_04/Exercise_04_05/Exercise_04_05.java

@@ -0,0 +1,45 @@
+package chapter_04;
+
+/**
+ * 5. Convert the following code so that it uses nested while statements instead
+ * of for statements:
+ * int s = 0;
+ * int t = 1;
+ * for (int i = 0; i < 10; i++)
+ * {
+ *  s = s + i;
+ *  for (int j = i; j > 0; j−−)
+ *  {
+ *  t = t * (j − i);
+ *  }
+ *  s = s * t;
+ *  System.out.println("T is " + t);
+ * }
+ * System.out.println("S is " + s);
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_05
+{
+    public static void main(String[] args)
+    {
+        int s = 0;
+        int t = 1;
+        int i = 0;
+        while (i < 10)
+        {
+            s = s + i;
+            int j = i;
+            while (j > 0)
+            {
+                t = t * (j - i);
+                j--;
+            }
+            s = s * t;
+            System.out.println("T is " + t);
+            i++;
+        }
+        System.out.println("S is " + s);
+    }
+}

chapter_04/Exercise_04_06/Exercise_04_06.java

@@ -0,0 +1,19 @@
+package chapter_04;
+
+/**
+ * 6. Write a for statement to compute the sum 1 + 1/2 + 1/3 + 1/4 + ... + 1/n
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_06
+{
+    public static void main(String[] args)
+    {
+       int n = 100;
+       double sum = 0;
+       for (int i = n; i > 0; i--)
+           sum += 1.0 / i;
+       System.out.println("The sum is " + sum);
+    }
+}

chapter_04/Exercise_04_07/Exercise_04_07.java

@@ -0,0 +1,19 @@
+package chapter_04;
+
+/**
+ * 7. Repeat the previous question, but use the comma operator and omit the
+ * for statement’s body
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_07
+{
+    public static void main(String[] args)
+    {
+       int n = 100;
+       double sum = 0;
+       for (int i = n; i > 0; sum += 1.0/i--);
+       System.out.println("The sum is " + sum);
+    }
+}

chapter_04/Exercise_04_08/Exercise_04_08.java

@@ -0,0 +1,21 @@
+package chapter_04;
+
+/**
+ * 8. Write a loop that will count the number of blank characters in a given
+ * string.
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_08
+{
+    public static void main(String[] args)
+    {
+        String word = "     Sharaf Qeshta     ";
+        int blanks = 0;
+        for (int i = 0; i < word.length(); i++)
+            blanks += ((word.charAt(i) + "").isBlank())? 1 : 0;
+
+        System.out.println("The number of blanks in " + word + " is " + blanks);
+    }
+}

chapter_04/Exercise_04_09/Exercise_04_09.java

@@ -0,0 +1,22 @@
+package chapter_04;
+
+/**
+ * 9. Write a loop that will create a new string that is the reverse of a given
+ * string.
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_09
+{
+    public static void main(String[] args)
+    {
+        String word = "Sharaf Qeshta";
+        String reverse = "";
+
+        for (int i = word.length()-1; i > -1; i--)
+            reverse += word.charAt(i);
+
+        System.out.println(reverse); // athseQ farahS
+    }
+}

chapter_04/Exercise_04_10/Exercise_04_10.java

@@ -0,0 +1,65 @@
+package chapter_04;
+
+import java.util.Scanner;
+
+/**
+ * 10. Write a program that will compute statistics for eight coin tosses. The user
+ * will enter either an h for heads or a t for tails for the eight tosses. The program
+ * will then display the total number and percentages of heads and tails. Use
+ * the increment operator to count each h and t that is entered. For example, a
+ * possible sample dialogue between the program and the user might be
+ * For each coin toss enter either h for heads or t for tails.
+ * First toss: h
+ * Second toss: t
+ * Third toss: t
+ * Fourth toss: h
+ * Fifth toss: t
+ * Sixth toss: h
+ * Seventh toss: t
+ * Eighth toss: t
+ * Number of heads: 3
+ * Number of tails: 5
+ * Percent heads: 37.5
+ * Percent tails: 62.5
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_10
+{
+    public static void main(String[] args)
+    {
+        Scanner scanner = new Scanner(System.in);
+        System.out.println("For each coin toss enter either h for heads or t for tails.");
+        int temp = 0, heads = 0, tails = 0;
+
+        System.out.print("First toss: ");
+        temp = (scanner.next().charAt(0) == 'h')? heads++ : tails++;
+
+        System.out.print("Second toss: ");
+        temp = (scanner.next().charAt(0) == 'h')? heads++ : tails++;
+
+        System.out.print("Third toss: ");
+        temp = (scanner.next().charAt(0) == 'h')? heads++ : tails++;
+
+        System.out.print("Fourth toss: ");
+        temp = (scanner.next().charAt(0) == 'h')? heads++ : tails++;
+
+        System.out.print("Fifth toss: ");
+        temp = (scanner.next().charAt(0) == 'h')? heads++ : tails++;
+
+        System.out.print("Sixth toss: ");
+        temp = (scanner.next().charAt(0) == 'h')? heads++ : tails++;
+
+        System.out.print("Seventh toss: ");
+        temp = (scanner.next().charAt(0) == 'h')? heads++ : tails++;
+
+        System.out.print("Eighth toss: ");
+        temp = (scanner.next().charAt(0) == 'h')? heads++ : tails++;
+
+        System.out.println("Number of heads: " + heads);
+        System.out.println("Number of tails: " + tails);
+        System.out.println("Percent heads: " + (heads/8.0) * 100);
+        System.out.println("Percent tails: " + (tails/8.0) * 100);
+    }
+}

chapter_04/Exercise_04_11/Exercise_04_11.java

@@ -0,0 +1,30 @@
+package chapter_04;
+
+/**
+ * 11. Suppose we attend a party. To be sociable, we will shake hands with
+ * everyone else. Write a fragment of code using a for statement that will
+ * compute the total number of handshakes that occur. (Hint: Upon
+ * arrival, each person shakes hands with everyone who is already there.
+ * Use the loop to find the total number of handshakes as each person
+ * arrives.)
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_11
+{
+    public static void main(String[] args)
+    {
+        int handShakes = 0;
+        int numberOfPeople = 5;
+        for (int i = 1; i <= numberOfPeople; i++)
+            // everytime we simulating that a new person came
+            // everyone came will shake hand with everyone in the party
+            handShakes += (i-1);
+
+        // there`s a simpler algorithm to calculate the handshakes
+        // which is (numberOfPeople * (numberOfPeople - 1)) / 2
+
+        System.out.println("If there`s " + numberOfPeople + " people then there`s " + handShakes + " handshakes");
+    }
+}

chapter_04/Exercise_04_13/Exercise_04_13.java

@@ -0,0 +1,42 @@
+package chapter_04;
+
+import java.util.Scanner;
+
+/**
+ * 13. Write a fragment of code that computes the final score of a bowling game.
+ * Use a loop to read the number of pins toppled by three players during five
+ * turns each. Display the final score afterward.
+ *
+ *
+ * @author Sharaf Qeshta
+ * */
+public class Exercise_04_13
+{
+    public static void main(String[] args)
+    {
+        int player1Scores = 0, player2Scores = 0, player3Scores = 0;
+        Scanner scanner = new Scanner(System.in);
+
+        for (int i = 1; i < 4; i++)
+        {
+            int playerScores = 0;
+            for (int j = 1; j < 5; j++)
+            {
+                System.out.println("Enter the number of pins toppled by player "
+                        + i + " at round " + j + ": ");
+                playerScores += scanner.nextInt();
+            }
+
+            if (i == 1)
+                player1Scores = playerScores;
+            else if (i == 2)
+                player2Scores = playerScores;
+            else
+                player3Scores = playerScores;
+        }
+
+        System.out.println("Player 1 scores " + player1Scores);
+        System.out.println("Player 2 scores " + player2Scores);
+        System.out.println("Player 3 scores " + player3Scores);
+    }
+}