Mergesort

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        int size = 5 ;
      double[] arrayList = new double[size];
      for(int i = 0 ; i < arrayList.length ; ++i){
          arrayList[i] = (Math.random()*1000);
      }

        mergeSort(arrayList,0,arrayList.length-1);
        print(arrayList);

    }
    public static void print(double []  arrayList){
        for(int i = 0 ; i < arrayList.length; ++i){
            System.out.println(arrayList[i]);
        }
    }
    public  static void mergeSort(double [] arr , int l , int r){
        if(l<r){
            int m = l+(r-l)/2;

            mergeSort(arr,l,m);
            mergeSort(arr,m+1,r);

            merge(arr,l , m , r);
        }

    }

    public  static void merge(double[] unsorted, int l , int m , int r){
        int i ,j ,k;
        int arr1 = m - l +1;
        int arr2 = r - m ;
        double [] left = new double[arr1];
        double [] right = new double[arr2];
        for(int f = 0 ; f < arr1 ; ++f){
            left[f] = unsorted[l+f];
        }
        for (int s = 0 ; s < arr2 ; ++s){
           right[s] = unsorted[m+1+s];
        }

        i = j = 0;
        k = l ;

        while(i < arr1 && j < arr2){
            if(left[i] <= right[j]){
                unsorted[k] = left[i];
                ++i;
            }
            else {
                unsorted[k]= right[j];
                ++j;
            }
            ++k;
        }

        while(i<arr1){
            unsorted[k] = left[i];
            ++i;++k;
        }
        while(j<arr2){
            unsorted[k] = right[j];
            ++j;++k;
        }


    }
}

MergeSort

# MergeSort in Python


def mergeSort(array):
    if len(array) > 1:

        #  r is the point where the array is divided into two subarrays
        r = len(array)//2
        L = array[:r]
        M = array[r:]

        # Sort the two halves
        mergeSort(L)
        mergeSort(M)

        i = j = k = 0

        # Until we reach either end of either L or M, pick larger among
        # elements L and M and place them in the correct position at A[p..r]
        while i < len(L) and j < len(M):
            if L[i] < M[j]:
                array[k] = L[i]
                i += 1
            else:
                array[k] = M[j]
                j += 1
            k += 1

        # When we run out of elements in either L or M,
        # pick up the remaining elements and put in A[p..r]
        while i < len(L):
            array[k] = L[i]
            i += 1
            k += 1

        while j < len(M):
            array[k] = M[j]
            j += 1
            k += 1


# Print the array
def printList(array):
    for i in range(len(array)):
        print(array[i], end=" ")
    print()


# Driver program
if __name__ == '__main__':
    array = [6, 5, 12, 10, 9, 1]

    mergeSort(array)

    print("Sorted array is: ")
    printList(array)

Source: programiz.com

Merge sort

def mergeSort(arr):
    if len(arr) > 1:
  
         # Finding the mid of the array
        mid = len(arr)//2
  
        # Dividing the array elements
        L = arr[:mid]
  
        # into 2 halves
        R = arr[mid:]
  
        # Sorting the first half
        mergeSort(L)
  
        # Sorting the second half
        mergeSort(R)
  
        i = j = k = 0
  
        # Copy data to temp arrays L[] and R[]
        while i < len(L) and j < len(R):
            if L[i] < R[j]:
                arr[k] = L[i]
                i += 1
            else:
                arr[k] = R[j]
                j += 1
            k += 1
  
        # Checking if any element was left
        while i < len(L):
            arr[k] = L[i]
            i += 1
            k += 1
  
        while j < len(R):
            arr[k] = R[j]
            j += 1
            k += 1

Merge sort

Step 1 − if it is only one element in the list it is already sorted, return.
Step 2 − divide the list recursively into two halves until it can no more be divided.
Step 3 − merge the smaller lists into new list in sorted order.

Source: tutorialspoint.com

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