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package Assignments.A4;
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public class Mergesort {
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// Merges two subarrays of arr[].
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// First subarray is arr[l..m]
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// Second subarray is arr[m+1..r]
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void merge(int[] list, int left, int mid, int right) {
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// Create temp arrays
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int[] sub1 = new int[mid - left + 1];
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int[] sub2 = new int[right - mid];
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// Copy data to temp arrays
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System.arraycopy(list, left, sub1, 0, sub1.length);
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System.arraycopy(list, mid + 1, sub2, 0, sub2.length);
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int l1 = 0;
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int l2 = 0;
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// Initial index of merged subarray array
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int k = left;
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while (l1 < sub1.length && l2 < sub2.length) {
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if (sub1[l1] <= sub2[l2]) {
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list[k] = sub1[l1];
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l1++;
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} else {
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list[k] = sub2[l2];
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l2++;
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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 (l1 < sub1.length) {
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list[k] = sub1[l1];
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l1++;
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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 (l2 < sub2.length) {
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list[k] = sub2[l2];
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l2++;
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k++;
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}
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}
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// Main function that sorts arr[l..r] using
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// merge()
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void sort(int[] list, int left, int right) {
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if (left < right) {
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// Find the middle point
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int m = left + (right - left) / 2;
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// Sort first and second halves
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sort(list, left, m);
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sort(list, m + 1, right);
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// Merge the sorted halves
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merge(list, left, m, right);
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}
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}
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// A utility function to print array of size n
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static void printArray(int[] list) {
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int n = list.length;
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for (int i = 0; i < n; ++i)
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System.out.print(list[i] + " ");
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System.out.println();
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}
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// Driver code
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public static void main(String[] args) {
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int[] arr = {12, 11, 13, 5, 6, 7};
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System.out.println("Given array is");
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printArray(arr);
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Mergesort ob = new Mergesort();
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ob.sort(arr, 0, arr.length - 1);
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System.out.println("\nSorted array is");
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printArray(arr);
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}
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}
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@ -1,71 +0,0 @@
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package Assignments.A4;
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public class Quicksort {
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/** Number of comparisons for the sorting alg. */
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public int comps = 0;
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/**
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* Sorts the provided list using quicksort.
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* @param list the list to be sorted.
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*/
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public void sort(int[] list) {
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if (list != null && list.length > 0) {
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this.comps = 0;
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quicksort(list, 0, list.length - 1);
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}
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}
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/**
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* This functions sorts the provided array (by reference) using quicksort algorithm.
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* <p>
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* It does this by while high is greater than low, it finds the partitioning index and then
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* calls quicksort again on the lower half and upper half.
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* </p>
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* @param list the list to be sorted.
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* @param low the lower bound of the list.
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* @param high the upper bound of the list.
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*/
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private void quicksort(int[] list, int low, int high) {
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if (low < high) {
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this.comps++;
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int pi = partition(list, low, high);
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quicksort(list, low, pi - 1);
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quicksort(list, pi + 1, high);
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}
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}
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/**
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* This function takes the last element as pivot, places the pivot element at its sorted position.
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* @param values the array to be sorted.
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* @param low the lower bound of the array.
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* @param high the upper bound of the array.
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* @return the partition index.
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*/
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private int partition(int[] values, int low, int high) {
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int pivot = values[high];
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int i = (low - 1);
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for (int j = low; j <= high - 1; j++) {
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if (values[j] < pivot) {
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i++;
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swap(values, i, j);
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}
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this.comps++;
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}
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swap(values, i + 1, high);
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return (i + 1);
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}
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/**
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* Abstracts teh swap function to make the code easier to follow.
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* @param values the array to be sorted.
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* @param i the first index to be swapped.
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* @param j the second index to be swapped.
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*/
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private void swap(int[] values, int i, int j) {
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int temp = values[i];
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values[i] = values[j];
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values[j] = temp;
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}
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}
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