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fixed merge sort #2202

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Merged
merged 2 commits into from
May 6, 2021
Merged

fixed merge sort #2202

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d95d2b9
reformat merge sort
realDuYuanChao May 6, 2021
9cc36e0
Formatted with Google Java Formatter
May 6, 2021
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50 changes: 23 additions & 27 deletions Sorts/MergeSort.java
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Original file line number Diff line number Diff line change
@@ -1,22 +1,18 @@
package Sorts;

import static Sorts.SortUtils.print;

/**
* This method implements the Generic Merge Sort
* Generic merge sort algorithm.
*
* @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
* Generic merge sort algorithm implements.
*
* @param unsorted the array which should be sorted
* @param <T> Comparable class
* @return sorted array
* @param unsorted the array which should be sorted.
* @param <T> Comparable class.
* @return sorted array.
*/
@Override
public <T extends Comparable<T>> T[] sort(T[] unsorted) {
Expand All @@ -25,29 +21,30 @@ public <T extends Comparable<T>> T[] sort(T[] unsorted) {
}

/**
* @param arr The array to be sorted
* @param left The first index of the array
* @param right The last index of the array Recursively sorts the array in increasing order
* @param arr the array to be sorted.
* @param left the first index of the array.
* @param right the last index of the array.
*/
private static <T extends Comparable<T>> void doSort(T[] arr, int left, int right) {
if (left < right) {
int mid = left + (right - left) / 2;
int mid = (left + right) >>> 1;
doSort(arr, left, mid);
doSort(arr, mid + 1, right);
merge(arr, left, mid, right);
}
}

/**
* This method implements the merge step of the merge sort
* Merges two parts of an array.
*
* @param arr The array to be sorted
* @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
* @param arr the array to be merged.
* @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, int left, int mid, int right) {
int length = right - left + 1;
@SuppressWarnings("unchecked")
T[] temp = (T[]) new Comparable[length];
int i = left;
int j = mid + 1;
Expand All @@ -72,21 +69,20 @@ private static <T extends Comparable<T>> void merge(T[] arr, int left, int mid,
System.arraycopy(temp, 0, arr, left, length);
}

// Driver program
/** Driver code */
public static void main(String[] args) {
MergeSort mergeSort = new MergeSort();

// Integer Input
Integer[] arr = {4, 23, 6, 78, 1, 54, 231, 9, 12};
MergeSort mergeSort = new MergeSort();
mergeSort.sort(arr);
for (int i = 0; i < arr.length - 1; ++i) {
assert arr[i] <= arr[i + 1];
}

// 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);
for (int i = 0; i < stringArray.length - 1; ++i) {
assert arr[i].compareTo(arr[i + 1]) <= 0;
}
}
}