12. Book Exercises

Chapter 12, exercises 23, 24, and 25. Write tests to prove that your work is correct. Those exercises, restated here, are:

Exercise 23: Rotate

1. public static int[] rotateLeft(int[] a): Rotate {0,1,2,3} to {1,2,3,0}.
2. public static int[] rotateRight(int[] a): Rotate {0,1,2,3} to {3,0,1,2}.
3. public static int[] rotate(int[] a, int amount): Rotate by amount to the right, so to the left when amount is negative.

Exercise 24: Add Digits

1. Add two positive numbers given by arrays representing the individual digits.

   public static int[] add(int[] a, int[] b)

   Example 923+94=1017:

   @Test
   public void test_add_1() {
       int[] a = {9,2,3};
       int[] b = {9,4};
       int[] ans = {1,0,1,7};
       assertArrayEquals(ans, add(a,b));
   }

Exercise 25: Average Two Largest

1. Find the average of the greatest two elements in an array.

   public static double largestAverage(int [] data)

   @Test
   public void test_largest_average() {
       int[] data = {100,40,90,30};
       assertEquals(95, largestAverage(data), 0.1);
   
       int[] fdata = {-1000,-30,-31,-80};
       assertEquals(-30.5, largestAverage(fdata), 0.1);
   
       int[] gdata = {100,100,50,40};
       assertEquals(100, largestAverage(gdata), 0.1);
   }