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60 lines (47 loc) · 1.36 KB
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package util;
/**
* Created by nikoo28 on 10/4/20 7:39 PM
*/
public class MergeSort {
public static void mergeSort(int[] arr, int numberOfElements) {
if (numberOfElements < 2) {
return;
}
// Find the middle position and create left and right partitions
int mid = numberOfElements/2;
int[] leftArr = new int[mid];
int[] rightArr = new int[numberOfElements - mid];
// Fill up the partitions
for (int i = 0; i < mid; i++) {
leftArr[i] = arr[i];
}
for (int i = mid; i < numberOfElements; i++) {
rightArr[i- mid] = arr[i];
}
// Apply merge sort on the left parition
mergeSort(leftArr, mid);
// Apply merge sort on the right partition
mergeSort(rightArr, numberOfElements - mid);
// Finally merge the partitions
merge(arr, leftArr, rightArr, mid, numberOfElements - mid);
}
private static void merge(int[] arr, int[] leftArr, int[] rightArr, int left, int right) {
int i = 0, j = 0, k = 0;
// Merge arrays based on the smaller values
while (i < left && j < right) {
if (leftArr[i] <= rightArr[j]) {
arr[k++] = leftArr[i++];
}
else {
arr[k++] = rightArr[j++];
}
}
// Fill out remaining values if any
while (i < left) {
arr[k++] = leftArr[i++];
}
while (j < right) {
arr[k++] = rightArr[j++];
}
}
}