👀 Views: 365 💬 Answers: 1 📅 Created: 2025-07-05

sorting merge-sort algorithms Java

I'm prototyping a solution and I've tried everything I can think of but I'm working on a personal project and I'm encountering an issue with my implementation of the merge sort algorithm in Java... I have noticed that when sorting particularly large arrays, the output is not as expected. Instead of a fully sorted array, I get a partially sorted array, particularly when elements are duplicated. Here's my current implementation: ```java public class MergeSort { public static void mergeSort(int[] array) { if (array.length < 2) { return; } int mid = array.length / 2; int[] left = new int[mid]; int[] right = new int[array.length - mid]; System.arraycopy(array, 0, left, 0, mid); System.arraycopy(array, mid, right, 0, array.length - mid); mergeSort(left); mergeSort(right); merge(array, left, right); } private static void merge(int[] array, int[] left, int[] right) { int i = 0, j = 0, k = 0; while (i < left.length && j < right.length) { if (left[i] <= right[j]) { array[k++] = left[i++]; } else { array[k++] = right[j++]; } } while (i < left.length) { array[k++] = left[i++]; } while (j < right.length) { array[k++] = right[j++]; } } } ``` I tested this implementation with arrays of size 10,000 and noticed that duplicates, specifically, cause issues in merging. For instance, for the input array `{5, 3, 8, 3, 9, 1, 5}`, the sorted output is sometimes missing some of the `5`s or `3`s. I suspected that the issue might be related to how I'm managing indices during the merge step, but I’ve double-checked that part. I also tried using a debugger, and while stepping through the code, I confirmed that both `left` and `right` arrays are filled correctly. I am using Java 11 and running this in a standard console application. Any insights or suggestions would be greatly appreciated! Am I missing something fundamental in the merge process, or could it be that the issue manifests only with certain data configurations? I'm on Ubuntu 20.04 using the latest version of Java. Any feedback is welcome! Thanks for any help you can provide! I've been using Java for about a year now. Could someone point me to the right documentation?