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improve logic of merge() function

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Evan Ferrao 2024-08-11 01:01:29 +05:30
parent 296ac7e47a
commit caf8723cba
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2 changed files with 180 additions and 92 deletions
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110
Sorting/MergeSort.java
View File

@ -1,5 +1,6 @@
// write a code of mergesort using function in java // write a code of mergesort using function in java
import java.util.ArrayList;
import java.util.Scanner; import java.util.Scanner;
public class MergeSort{ public class MergeSort{
// use notation beginning, mid and end // use notation beginning, mid and end
@ -34,52 +35,87 @@ public class MergeSort{
merge(arr, beginning, mid, end); merge(arr, beginning, mid, end);
} }
} }
static void merge(int arr[], int beginning, int mid, int end){ // static void merge(int arr[], int beginning, int mid, int end){
// find the size of two subarrays to be merged // // find the size of two subarrays to be merged
int n1 = mid - beginning + 1; // int n1 = mid - beginning + 1;
int n2 = end - mid; // int n2 = end - mid;
// create temp arrays // // create temp arrays
int L[] = new int[n1]; // int L[] = new int[n1];
int R[] = new int[n2]; // int R[] = new int[n2];
// copy data to temp arrays // // copy data to temp arrays
for(int i = 0; i < n1; i++){ // for(int i = 0; i < n1; i++){
L[i] = arr[beginning + i]; // L[i] = arr[beginning + i];
} // }
for(int j = 0; j < n2; j++){ // for(int j = 0; j < n2; j++){
R[j] = arr[mid + 1 + j]; // R[j] = arr[mid + 1 + j];
} // }
// merge the temp arrays // // merge the temp arrays
// initial indexes of first and second subarrays // // initial indexes of first and second subarrays
int i = 0, j = 0; // int i = 0, j = 0;
// initial index of merged subarray array // // initial index of merged subarray array
int k = beginning; // int k = beginning;
while(i < n1 && j < n2){ // while(i < n1 && j < n2){
if(L[i] <= R[j]){ // if(L[i] <= R[j]){
arr[k] = L[i]; // arr[k] = L[i];
i++; // i++;
}else{ // }else{
arr[k] = R[j]; // arr[k] = R[j];
j++; // j++;
// }
// k++;
// }
// // copy remaining elements of L[] if any
// while(i < n1){
// arr[k] = L[i];
// i++;
// k++;
// }
// // copy remaining elements of R[] if any
// while(j < n2){
// arr[k] = R[j];
// j++;
// k++;
// }
// }
static void merge(int[] arr, int low, int mid, int high) {
ArrayList<Integer> temp = new ArrayList<>(); // temporary array
int left = low; // starting index of left half of arr
int right = mid + 1; // starting index of right half of arr
//storing elements in the temporary array in a sorted manner//
while (left <= mid && right <= high) {
if (arr[left] <= arr[right]) {
temp.add(arr[left]);
left++;
} else {
temp.add(arr[right]);
right++;
} }
k++;
} }
// copy remaining elements of L[] if any // if elements on the left half are still left //
while(i < n1){
arr[k] = L[i]; while (left <= mid) {
i++; temp.add(arr[left]);
k++; left++;
} }
// copy remaining elements of R[] if any // if elements on the right half are still left //
while(j < n2){ while (right <= high) {
arr[k] = R[j]; temp.add(arr[right]);
j++; right++;
k++; }
// transfering all elements from temporary to arr //
for (int i = low; i <= high; i++) {
arr[i] = temp.get(i - low);
} }
} }

162
Sorting/VisualMergeSort.java
View File

@ -1,3 +1,5 @@
import java.util.ArrayList;
public class VisualMergeSort { public class VisualMergeSort {
static String RESET = "\u001B[0m"; static String RESET = "\u001B[0m";
static String RED = "\u001B[31m"; static String RED = "\u001B[31m";
@ -56,71 +58,121 @@ public class VisualMergeSort {
} }
// Method to merge two sorted subarrays with level parameter // Method to merge two sorted subarrays with level parameter
public static void merge(int[] array, int left, int mid, int right, int currentLevel) { // public static void merge(int[] array, int left, int mid, int right, int currentLevel) {
// 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);
// System.out.printf("Subarrays before merge: ");
// printArray(array, left, mid);
// System.out.printf("and ");
// printArray(array, mid + 1, right);
// System.out.println();
// // Sizes of the two subarrays to merge
// int n1 = mid - left + 1;
// int n2 = right - mid;
// // Create temporary arrays
// int[] leftArray = new int[n1];
// int[] rightArray = new int[n2];
// // Copy data to temporary arrays
// for (int i = 0; i < n1; i++) {
// leftArray[i] = array[left + i];
// }
// for (int j = 0; j < n2; j++) {
// rightArray[j] = array[mid + 1 + j];
// }
// // Display temporary arrays
// System.out.printf("Left array: ");
// printArray(leftArray);
// System.out.printf("Right array: ");
// printArray(rightArray);
// // Merge the temporary arrays back into the original array
// int i = 0, j = 0;
// int k = left;
// while (i < n1 && j < n2) {
// if (leftArray[i] <= rightArray[j]) {
// array[k] = leftArray[i];
// i++;
// } else {
// array[k] = rightArray[j];
// j++;
// }
// System.out.printf("Placing %d at index %d\n", array[k], k);
// k++;
// }
// // Copy remaining elements of leftArray[], if any
// while (i < n1) {
// array[k] = leftArray[i];
// System.out.printf("Placing %d at index %d\n", array[k], k);
// i++;
// k++;
// }
// // Copy remaining elements of rightArray[], if any
// while (j < n2) {
// array[k] = rightArray[j];
// System.out.printf("Placing %d at index %d\n", array[k], k);
// j++;
// k++;
// }
// // Display the merged array
// System.out.printf("Merged array from index %d to %d: ", left, right);
// printArray(array, left, right);
// System.out.println();
// }
public static void merge(int[] arr, int low, int mid, int high, int currentLevel) {
ArrayList<Integer> temp = new ArrayList<>(); // temporary array
int left = low; // starting index of left half of arr
int right = mid + 1; // starting index of right half of arr
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); 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);
System.out.printf("Subarrays before merge: "); System.out.printf("Subarrays before merge: ");
printArray(array, left, mid); printArray(arr, left, mid);
printArray(array, mid + 1, right); System.out.printf("and ");
printArray(arr, mid + 1, right);
System.out.println(); System.out.println();
// Sizes of the two subarrays to merge // Storing elements in the temporary array in a sorted manner
int n1 = mid - left + 1; while (left <= mid && right <= high) {
int n2 = right - mid; if (arr[left] <= arr[right]) {
temp.add(arr[left]);
// Create temporary arrays left++;
int[] leftArray = new int[n1];
int[] rightArray = new int[n2];
// Copy data to temporary arrays
for (int i = 0; i < n1; i++) {
leftArray[i] = array[left + i];
}
for (int j = 0; j < n2; j++) {
rightArray[j] = array[mid + 1 + j];
}
// Display temporary arrays
System.out.printf("Left array: ");
printArray(leftArray);
System.out.printf("Right array: ");
printArray(rightArray);
// Merge the temporary arrays back into the original array
int i = 0, j = 0;
int k = left;
while (i < n1 && j < n2) {
if (leftArray[i] <= rightArray[j]) {
array[k] = leftArray[i];
i++;
} else { } else {
array[k] = rightArray[j]; temp.add(arr[right]);
j++; right++;
} }
System.out.printf("Placing %d at index %d\n", array[k], k); System.out.printf("Placing %d at index %d\n", temp.get(temp.size() - 1), temp.size() - 1);
k++;
} }
// Copy remaining elements of leftArray[], if any // If elements on the left half are still left
while (i < n1) { while (left <= mid) {
array[k] = leftArray[i]; temp.add(arr[left]);
System.out.printf("Placing %d at index %d\n", array[k], k); System.out.printf("Placing %d at index %d\n", temp.get(temp.size() - 1), temp.size() - 1);
i++; left++;
k++;
} }
// Copy remaining elements of rightArray[], if any // If elements on the right half are still left
while (j < n2) { while (right <= high) {
array[k] = rightArray[j]; temp.add(arr[right]);
System.out.printf("Placing %d at index %d\n", array[k], k); System.out.printf("Placing %d at index %d\n", temp.get(temp.size() - 1), temp.size() - 1);
j++; right++;
k++;
} }
// Display the merged array // Transferring all elements from temporary to arr
System.out.printf("Merged array from index %d to %d: ", left, right); for (int i = low; i <= high; i++) {
printArray(array, left, right); arr[i] = temp.get(i - low);
}
System.out.printf("Merged array from index %d to %d: ", low, high); // Correct indices
printArray(arr, low, high); // Correct indices
System.out.println(); System.out.println();
} }
// Utility method to print the array // Utility method to print the array
public static void printArray(int[] array) { public static void printArray(int[] array) {