mirror of https://github.com/evanferrao/dsa
improve logic of merge() function
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@ -1,5 +1,6 @@
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// write a code of mergesort using function in java
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import java.util.ArrayList;
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import java.util.Scanner;
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public class MergeSort{
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// use notation beginning, mid and end
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@ -34,52 +35,87 @@ public class MergeSort{
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merge(arr, beginning, mid, end);
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}
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}
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static void merge(int arr[], int beginning, int mid, int end){
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// find the size of two subarrays to be merged
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int n1 = mid - beginning + 1;
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int n2 = end - mid;
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// static void merge(int arr[], int beginning, int mid, int end){
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// // find the size of two subarrays to be merged
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// int n1 = mid - beginning + 1;
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// int n2 = end - mid;
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// create temp arrays
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int L[] = new int[n1];
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int R[] = new int[n2];
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// // create temp arrays
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// int L[] = new int[n1];
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// int R[] = new int[n2];
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// copy data to temp arrays
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for(int i = 0; i < n1; i++){
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L[i] = arr[beginning + i];
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}
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for(int j = 0; j < n2; j++){
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R[j] = arr[mid + 1 + j];
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}
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// // copy data to temp arrays
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// for(int i = 0; i < n1; i++){
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// L[i] = arr[beginning + i];
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// }
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// for(int j = 0; j < n2; j++){
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// R[j] = arr[mid + 1 + j];
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// }
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// merge the temp arrays
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// initial indexes of first and second subarrays
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int i = 0, j = 0;
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// // merge the temp arrays
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// // initial indexes of first and second subarrays
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// int i = 0, j = 0;
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// initial index of merged subarray array
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int k = beginning;
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while(i < n1 && j < n2){
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if(L[i] <= R[j]){
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arr[k] = L[i];
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i++;
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}else{
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arr[k] = R[j];
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j++;
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// // initial index of merged subarray array
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// int k = beginning;
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// while(i < n1 && j < n2){
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// if(L[i] <= R[j]){
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// arr[k] = L[i];
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// i++;
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// }else{
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// arr[k] = R[j];
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// j++;
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// }
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// k++;
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// }
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// // copy remaining elements of L[] if any
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// while(i < n1){
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// arr[k] = L[i];
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// i++;
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// k++;
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// }
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// // copy remaining elements of R[] if any
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// while(j < n2){
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// arr[k] = R[j];
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// j++;
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// k++;
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// }
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// }
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static void merge(int[] arr, int low, int mid, int high) {
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ArrayList<Integer> temp = new ArrayList<>(); // temporary array
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int left = low; // starting index of left half of arr
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int right = mid + 1; // starting index of right half of arr
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//storing elements in the temporary array in a sorted manner//
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while (left <= mid && right <= high) {
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if (arr[left] <= arr[right]) {
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temp.add(arr[left]);
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left++;
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} else {
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temp.add(arr[right]);
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right++;
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}
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k++;
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}
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// copy remaining elements of L[] if any
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while(i < n1){
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arr[k] = L[i];
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i++;
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k++;
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// if elements on the left half are still left //
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while (left <= mid) {
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temp.add(arr[left]);
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left++;
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}
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// copy remaining elements of R[] if any
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while(j < n2){
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arr[k] = R[j];
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j++;
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k++;
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// if elements on the right half are still left //
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while (right <= high) {
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temp.add(arr[right]);
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right++;
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}
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// transfering all elements from temporary to arr //
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for (int i = low; i <= high; i++) {
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arr[i] = temp.get(i - low);
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}
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}
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@ -1,3 +1,5 @@
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import java.util.ArrayList;
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public class VisualMergeSort {
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static String RESET = "\u001B[0m";
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static String RED = "\u001B[31m";
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@ -56,71 +58,121 @@ public class VisualMergeSort {
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}
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// Method to merge two sorted subarrays with level parameter
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public static void merge(int[] array, int left, int mid, int right, int currentLevel) {
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// public static void merge(int[] array, int left, int mid, int right, int currentLevel) {
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// System.out.printf("%sMerging subarrays from index %d to %d and %d to %d with level %d%s\n", UNDERLINE, left, mid, mid + 1, right, currentLevel, RESET);
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// System.out.printf("Subarrays before merge: ");
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// printArray(array, left, mid);
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// System.out.printf("and ");
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// printArray(array, mid + 1, right);
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// System.out.println();
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// // Sizes of the two subarrays to merge
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// int n1 = mid - left + 1;
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// int n2 = right - mid;
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// // Create temporary arrays
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// int[] leftArray = new int[n1];
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// int[] rightArray = new int[n2];
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// // Copy data to temporary arrays
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// for (int i = 0; i < n1; i++) {
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// leftArray[i] = array[left + i];
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// }
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// for (int j = 0; j < n2; j++) {
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// rightArray[j] = array[mid + 1 + j];
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// }
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// // Display temporary arrays
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// System.out.printf("Left array: ");
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// printArray(leftArray);
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// System.out.printf("Right array: ");
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// printArray(rightArray);
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// // Merge the temporary arrays back into the original array
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// int i = 0, j = 0;
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// int k = left;
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// while (i < n1 && j < n2) {
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// if (leftArray[i] <= rightArray[j]) {
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// array[k] = leftArray[i];
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// i++;
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// } else {
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// array[k] = rightArray[j];
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// j++;
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// }
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// System.out.printf("Placing %d at index %d\n", array[k], k);
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// k++;
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// }
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// // Copy remaining elements of leftArray[], if any
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// while (i < n1) {
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// array[k] = leftArray[i];
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// System.out.printf("Placing %d at index %d\n", array[k], k);
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// i++;
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// k++;
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// }
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// // Copy remaining elements of rightArray[], if any
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// while (j < n2) {
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// array[k] = rightArray[j];
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// System.out.printf("Placing %d at index %d\n", array[k], k);
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// j++;
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// k++;
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// }
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// // Display the merged array
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// System.out.printf("Merged array from index %d to %d: ", left, right);
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// printArray(array, left, right);
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// System.out.println();
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// }
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public static void merge(int[] arr, int low, int mid, int high, int currentLevel) {
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ArrayList<Integer> temp = new ArrayList<>(); // temporary array
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int left = low; // starting index of left half of arr
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int right = mid + 1; // starting index of right half of arr
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System.out.printf("%sMerging subarrays from index %d to %d and %d to %d with level %d%s\n", UNDERLINE, left, mid, mid + 1, right, currentLevel, RESET);
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System.out.printf("Subarrays before merge: ");
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printArray(array, left, mid);
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printArray(array, mid + 1, right);
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printArray(arr, left, mid);
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System.out.printf("and ");
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printArray(arr, mid + 1, right);
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System.out.println();
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// Sizes of the two subarrays to merge
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int n1 = mid - left + 1;
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int n2 = right - mid;
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// Create temporary arrays
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int[] leftArray = new int[n1];
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int[] rightArray = new int[n2];
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// Copy data to temporary arrays
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for (int i = 0; i < n1; i++) {
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leftArray[i] = array[left + i];
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}
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for (int j = 0; j < n2; j++) {
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rightArray[j] = array[mid + 1 + j];
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}
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// Display temporary arrays
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System.out.printf("Left array: ");
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printArray(leftArray);
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System.out.printf("Right array: ");
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printArray(rightArray);
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// Merge the temporary arrays back into the original array
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int i = 0, j = 0;
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int k = left;
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while (i < n1 && j < n2) {
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if (leftArray[i] <= rightArray[j]) {
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array[k] = leftArray[i];
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i++;
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// Storing elements in the temporary array in a sorted manner
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while (left <= mid && right <= high) {
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if (arr[left] <= arr[right]) {
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temp.add(arr[left]);
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left++;
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} else {
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array[k] = rightArray[j];
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j++;
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temp.add(arr[right]);
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right++;
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}
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System.out.printf("Placing %d at index %d\n", array[k], k);
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k++;
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System.out.printf("Placing %d at index %d\n", temp.get(temp.size() - 1), temp.size() - 1);
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}
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// Copy remaining elements of leftArray[], if any
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while (i < n1) {
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array[k] = leftArray[i];
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System.out.printf("Placing %d at index %d\n", array[k], k);
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i++;
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k++;
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// If elements on the left half are still left
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while (left <= mid) {
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temp.add(arr[left]);
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System.out.printf("Placing %d at index %d\n", temp.get(temp.size() - 1), temp.size() - 1);
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left++;
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}
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// Copy remaining elements of rightArray[], if any
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while (j < n2) {
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array[k] = rightArray[j];
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System.out.printf("Placing %d at index %d\n", array[k], k);
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j++;
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k++;
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// If elements on the right half are still left
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while (right <= high) {
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temp.add(arr[right]);
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System.out.printf("Placing %d at index %d\n", temp.get(temp.size() - 1), temp.size() - 1);
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right++;
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}
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// Display the merged array
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System.out.printf("Merged array from index %d to %d: ", left, right);
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printArray(array, left, right);
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// Transferring all elements from temporary to arr
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for (int i = low; i <= high; i++) {
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arr[i] = temp.get(i - low);
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}
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System.out.printf("Merged array from index %d to %d: ", low, high); // Correct indices
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printArray(arr, low, high); // Correct indices
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System.out.println();
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}
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// Utility method to print the array
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public static void printArray(int[] array) {
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