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MergeSort.java
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100 lines (83 loc) · 2.79 KB
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package Sorts;
import static Sorts.SortUtils.print;
/**
* This method implements the Generic Merge Sort
*
* @author Varun Upadhyay (https://github.com/varunu28)
* @author Podshivalov Nikita (https://github.com/nikitap492)
* @see SortAlgorithm
*/
class MergeSort implements SortAlgorithm {
/**
* This method implements the Generic Merge Sort
*
* @param unsorted the array which should be sorted
* @param <T> Comparable class
* @return sorted array
*/
@Override
@SuppressWarnings("unchecked")
public <T extends Comparable<T>> T[] sort(T[] unsorted) {
T[] tmp = (T[]) new Comparable[unsorted.length];
doSort(unsorted, tmp, 0, unsorted.length - 1);
return unsorted;
}
/**
* @param arr The array to be sorted
* @param temp The copy of the actual array
* @param left The first index of the array
* @param right The last index of the array
* Recursively sorts the array in increasing order
**/
private static <T extends Comparable<T>> void doSort(T[] arr, T[] temp, int left, int right) {
if (left < right) {
int mid = left + (right - left) / 2;
doSort(arr, temp, left, mid);
doSort(arr, temp, mid + 1, right);
merge(arr, temp, left, mid, right);
}
}
/**
* This method implements the merge step of the merge sort
*
* @param arr The array to be sorted
* @param temp The copy of the actual array
* @param left The first index of the array
* @param mid The middle index of the array
* @param right The last index of the array
* merges two parts of an array in increasing order
**/
private static <T extends Comparable<T>> void merge(T[] arr, T[] temp, int left, int mid, int right) {
System.arraycopy(arr, left, temp, left, right - left + 1);
int i = left;
int j = mid + 1;
int k = left;
while (i <= mid && j <= right) {
if (temp[i].compareTo(temp[j]) <= 0) {
arr[k++] = temp[i++];
} else {
arr[k++] = temp[j++];
}
}
while (i <= mid) {
arr[k++] = temp[i++];
}
while (j <= right) {
arr[k++] = temp[j++];
}
}
// Driver program
public static void main(String[] args) {
// Integer Input
Integer[] arr = {4, 23, 6, 78, 1, 54, 231, 9, 12};
MergeSort mergeSort = new MergeSort();
mergeSort.sort(arr);
// Output => 1 4 6 9 12 23 54 78 231
print(arr);
// String Inpu
String[] stringArray = {"c", "a", "e", "b", "d"};
mergeSort.sort(stringArray);
//Output => a b c d e
print(stringArray);
}
}