👀 Views: 26 💬 Answers: 1 📅 Created: 2025-06-06

java sorting merge-sort Java

I've spent hours debugging this and I am implementing the Merge Sort algorithm in Java, but I've encountered unexpected behavior with certain input patterns... The code seems to work fine for randomly generated arrays and those with distinct elements, but when I test it with arrays containing repeated elements, it sometimes returns an array that is not fully sorted. Here's a snippet of my implementation: ```java public class MergeSort { public static void mergeSort(int[] array) { if (array.length < 2) { return; } int mid = array.length / 2; int[] left = Arrays.copyOfRange(array, 0, mid); int[] right = Arrays.copyOfRange(array, mid, array.length); 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++]; } } } ``` When I run this code with the input `int[] testArray = {5, 3, 5, 2, 5, 1};`, it returns an output of `[1, 2, 3, 5, 5, 5]`, which is correct, but when I try with `int[] testArray = {5, 5, 5, 2, 5, 1};`, the output is `[1, 2, 5, 5, 5, 5]`. The order of the repeated elements should remain the same, but it appears to be unstable in this case. I have read that Merge Sort is supposed to be stable when implemented correctly, so I'm unsure what goes wrong. I've tried debugging with print statements, and the merging process seems fine, but the order of elements is not preserved for repeated values. I’m using Java 17. Any insights on why this might be happening or how I could ensure the stability of my Merge Sort implementation? I'm working with Java in a Docker container on CentOS. I'd really appreciate any guidance on this.