Step by step analysis of the implementation steps of Java merge sort

Step by step analysis of the implementation process of Java merge sort code

Introduction:
Merge sort is a classic divide and conquer algorithm, which divides an array into two smaller ones arrays, then sort the two arrays separately, and finally merge the two sorted arrays into an ordered array. In this article, we will step by step analyze the implementation process of merge sort in Java and provide specific code examples.

1. Basic idea:
   The basic idea of merging sort is to recursively split the array to be sorted into two smaller sub-arrays, and then sort the two sub-arrays and merge them is an ordered array. This process will continue recursively until the smallest subarray has only one element, and then the sorting is completed by merging these ordered subarrays.
2. Implementation process:
   The following is the implementation process of merge sort in Java:

class MergeSort { // 归并排序函数 public void mergeSort(int[] array, int left, int right) { if (left < right) { // 找出中点 int mid = (left + right) / 2; // 递归排序左半部分和右半部分 mergeSort(array, left, mid); mergeSort(array, mid + 1, right); // 合并排序好的左半部分和右半部分 merge(array, left, mid, right); } } // 合并函数 public void merge(int[] array, int left, int mid, int right) { // 定义临时数组来存储合并后的数组 int[] temp = new int[right - left + 1]; int i = left; int j = mid + 1; int k = 0; // 将左半部分和右半部分按顺序合并到临时数组中 while (i <= mid && j <= right) { if (array[i] <= array[j]) { temp[k++] = array[i++]; } else { temp[k++] = array[j++]; } } // 将剩余的元素复制到临时数组中 while (i <= mid) { temp[k++] = array[i++]; } while (j <= right) { temp[k++] = array[j++]; } // 将临时数组中的元素复制回原数组 for (int m = 0; m < temp.length; m++) { array[left + m] = temp[m]; } } // 测试 public static void main(String[] args) { int[] array = {8, 5, 2, 9, 5, 6, 3}; int n = array.length; MergeSort mergeSort = new MergeSort(); mergeSort.mergeSort(array, 0, n - 1); System.out.println("归并排序结果："); for (int i = 0; i < n; i++) { System.out.print(array[i] + " "); } } }

3. Example description:
   In the above code,mergeSortMethod is the entry function of merge sort, which receives an array to be sorted and the left and right boundaries of the array. In this function, we first determine whether the left and right boundaries meet the conditions for splitting (i.e.left ). If so, find the midpoint of the array and call mergeSort## recursively. #Function sorts the left half and right half. Finally, call themergefunction to merge the two ordered subarrays into one ordered array.