

Program: Implement merge sort in java.
Merge sort is a divide and conquer algorithm.
Steps to implement Merge Sort:
1) Divide the unsorted array into n partitions, each partition contains 1 element. Here the one element is considered as
sorted.
2) Repeatedly merge partitioned units to produce new sublists until there is only 1 sublist remaining. This will be the
sorted list at the end.
Merge sort is a fast, stable sorting routine with guaranteed O(n*log(n)) efficiency. When sorting arrays,
merge sort requires additional scratch space proportional to the size of the input array. Merge sort is relatively simple
to code and offers performance typically only slightly below that of quicksort.
package com.java2novice.sorting;
public class MyMergeSort {
private int[] array;
private int[] tempMergArr;
private int length;
public static void main(String a[]){
int[] inputArr = {45,23,11,89,77,98,4,28,65,43};
MyMergeSort mms = new MyMergeSort();
mms.sort(inputArr);
for(int i:inputArr){
System.out.print(i);
System.out.print(" ");
}
}
public void sort(int inputArr[]) {
this.array = inputArr;
this.length = inputArr.length;
this.tempMergArr = new int[length];
doMergeSort(0, length  1);
}
private void doMergeSort(int lowerIndex, int higherIndex) {
if (lowerIndex < higherIndex) {
int middle = lowerIndex + (higherIndex  lowerIndex) / 2;
// Below step sorts the left side of the array
doMergeSort(lowerIndex, middle);
// Below step sorts the right side of the array
doMergeSort(middle + 1, higherIndex);
// Now merge both sides
mergeParts(lowerIndex, middle, higherIndex);
}
}
private void mergeParts(int lowerIndex, int middle, int higherIndex) {
for (int i = lowerIndex; i <= higherIndex; i++) {
tempMergArr[i] = array[i];
}
int i = lowerIndex;
int j = middle + 1;
int k = lowerIndex;
while (i <= middle && j <= higherIndex) {
if (tempMergArr[i] <= tempMergArr[j]) {
array[k] = tempMergArr[i];
i++;
} else {
array[k] = tempMergArr[j];
j++;
}
k++;
}
while (i <= middle) {
array[k] = tempMergArr[i];
k++;
i++;
}
}
}


Output: 
4 11 23 28 43 45 65 77 89 98





Java Sorting Algorithms Examples
 Implement bubble sort in java.
 Implement selection sort in java.
 Implement insertion sort in java.
 Implement quick sort in java.
 Implement merge sort in java.



What is wrapper class?
Everything in java is an object, except primitives. Primitives are
int, short, long, boolean, etc. Since they are not objects, they cannot
return as objects, and collection of objects. To support this, java provides
wrapper classes to move primitives to objects. Some of the wrapper classes
are Integer, Long, Boolean, etc.
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 Spanish Proverb
