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Split and then add both sides of an array together in Java

The challenge

You will receive an array as a parameter that contains 1 or more integers and a number n.

Here is a little visualization of the process:

  • Step 1: Split the array in two:[1, 2, 5, 7, 2, 3, 5, 7, 8] / \ [1, 2, 5, 7] [2, 3, 5, 7, 8]
  • Step 2: Put the arrays on top of each other: [1, 2, 5, 7] [2, 3, 5, 7, 8]
  • Step 3: Add them together:[2, 4, 7, 12, 15]

Repeat the above steps n times or until there is only one number left, and then return the array.

Examples

Input: arr=[4, 2, 5, 3, 2, 5, 7], n=2 Round 1 ------- step 1: [4, 2, 5] [3, 2, 5, 7] step 2: [4, 2, 5] [3, 2, 5, 7] step 3: [3, 6, 7, 12] Round 2 ------- step 1: [3, 6] [7, 12] step 2: [3, 6] [7, 12] step 3: [10, 18] Result: [10, 18]
Code language: HTTP (http)

The solution in Java code

Option 1:

import static java.util.Arrays.copyOfRange; class Solution { static int[] splitAndAdd(int[] numbers, int n) { if (numbers.length > 1 && n > ) { int[] half = copyOfRange(numbers, numbers.length / 2, numbers.length); for (int i = ; i < numbers.length / 2; i++) { half[numbers.length % 2 > ? i + 1 : i] += numbers[i]; } return splitAndAdd(half, n - 1); } return numbers; } }
Code language: Java (java)

Option 2:

public class Solution { public static int[] splitAndAdd(int[] arr, int n) { if (n<= || arr.length==1) return arr; int len = arr.length/2; int[] arr1 = new int[len], arr2 = new int[arr.length-len]; System.arraycopy(arr, , arr1, , len); System.arraycopy(arr, len, arr2, , arr.length-len); int i = arr2.length - arr1.length; for (int a:arr1) arr2[i++] += a; return splitAndAdd(arr2, n-1); } }
Code language: Java (java)

Option 3:

public class Solution { public static int[] splitAndAdd(int[] numbers, int n) { if (n == ) return numbers; final int len = numbers.length; final int next[] = new int[(len+1)/2]; for (int i = ; i < next.length; i++) next[i] += numbers[len/2+i]; for (int i = len/2-1, j=next.length-1; i >= ; i--,j--) next[j] += numbers[i]; return splitAndAdd(next, n-1); } }
Code language: Java (java)

Test cases to validate our solution

import org.junit.Test; import static org.junit.Assert.assertEquals; import org.junit.runners.JUnit4; import java.util.*; public class TestClass { @Test public void splitAndAdd() throws Exception { int[] expected = new int[]{5,10}; int[] input = Solution.splitAndAdd(new int[]{1,2,3,4,5},2); assertEquals(Arrays.toString(expected), Arrays.toString(input)); expected = new int[]{15}; input = Solution.splitAndAdd(new int[]{1,2,3,4,5},3); assertEquals(Arrays.toString(expected),Arrays.toString(input)); expected = new int[]{15}; input = Solution.splitAndAdd(new int[]{15},3); assertEquals(Arrays.toString(expected),Arrays.toString(input)); expected = new int[]{183, 125}; input = Solution.splitAndAdd(new int[]{32,45,43,23,54,23,54,34},2); assertEquals(Arrays.toString(expected),Arrays.toString(input)); expected = new int[]{32,45,43,23,54,23,54,34}; input = Solution.splitAndAdd(new int[]{32,45,43,23,54,23,54,34},); assertEquals(Arrays.toString(expected),Arrays.toString(input)); expected = new int[]{305, 1195}; input = Solution.splitAndAdd(new int[]{3,234,25,345,45,34,234,235,345},3); assertEquals(Arrays.toString(expected),Arrays.toString(input)); expected = new int[]{1040, 7712}; input = Solution.splitAndAdd(new int[]{3,234,25,345,45,34,234,235,345,34,534,45,645,645,645,4656,45,3},4); assertEquals(Arrays.toString(expected),Arrays.toString(input)); expected = new int[]{79327}; input = Solution.splitAndAdd(new int[]{23,345,345,345,34536,567,568,6,34536,54,7546,456},20); assertEquals(Arrays.toString(expected),Arrays.toString(input)); } }
Code language: Java (java)

See also  How to get the Sum of the First nth Term of a Series in Java
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