/* * This program generates the alternating sum of double numbers stored in an array * For example, if the array contains 5 3 8 4 then the alternating sum is: 5-3+8-4 = 6 * the elem = 5 is at index 0 in the array (even index), elem 3 is at index 1 (odd index) etc * * Difficulty: Easy */ public class AlternatingSum { /** Computes the alternating sum of the values in an array list @param data an array list of values @return the alternating sum of the values in data */ public static int alternatingSum(int[] data) { //-----------Start below here. To do: approximate lines of code = 1 // Declare an integer variable sum to hold the sum and initialize it //-----------------End here. Please do not remove this comment. Reminder: no changes outside the todo regions. //-----------Start below here. To do: approximate lines of code = 5 // Use a for loop to go through each integer element in the array data[] // if the element is in an even location in the array (i.e. index 0 2 4 6 8 ...) then add it to sum // else subtract it from sum //-----------------End here. Please do not remove this comment. Reminder: no changes outside the todo regions. return sum; } public static void main(String[] args) { int[] data = { 1, 4, 9, 16, 9, 7, 4, 9, 11 }; int total = alternatingSum(data); System.out.println("Alternating sum: " + total); System.out.println("Expected: Alternating sum: -2"); int[] data1 = { 5, 3, 8, 4 }; total = alternatingSum(data1); System.out.println("Alternating sum: " + total); System.out.println("Expected: Alternating sum: 6"); int[] data2 = { 0 }; total = alternatingSum(data2); System.out.println("Alternating sum: " + total); System.out.println("Expected: Alternating sum: 0"); } }