merge sort implementation in c++ code example

Example 1: Merge sort in c++

#include <iostream>
using namespace std;
 

void merge(int arr[], int l, int m, int r)
{
    int n1 = m - l + 1;
    int n2 = r - m;
 
 
    int L[n1], R[n2];
 
   
    for (int i = 0; i < n1; i++)
        L[i] = arr[l + i];
    for (int j = 0; j < n2; j++)
        R[j] = arr[m + 1 + j];

 
    int i = 0;
 
    
    int j = 0;
 
    
    int k = l;
 
    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) {
            arr[k] = L[i];
            i++;
        }
        else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }
 
  
    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }
 
   
    while (j < n2) {
        arr[k] = R[j];
        j++;
        k++;
    }
}
 

void mergeSort(int arr[],int l,int r){
    if(l>=r){
        return;
    }
    int m = (l+r-1)/2;
    mergeSort(arr,l,m);
    mergeSort(arr,m+1,r);
    merge(arr,l,m,r);
}
 

void printArray(int A[], int size)
{
    for (int i = 0; i < size; i++)
        cout << A[i] << " ";
}
 

int main()
{
    int arr[] = { 12, 11, 13, 5, 6, 7 };
    int arr_size = sizeof(arr) / sizeof(arr[0]);
 
    cout << "Given array is \n";
    printArray(arr, arr_size);
 
    mergeSort(arr, 0, arr_size - 1);
 
    cout << "\nSorted array is \n";
    printArray(arr, arr_size);
    return 0;
}

Example 2: merge sort algo

def mergeSort(arr): 
    if len(arr) >1: 
        mid = len(arr)//2 # Finding the mid of the array 
        L = arr[:mid] # Dividing the array elements  
        R = arr[mid:] # into 2 halves 
  
        mergeSort(L) # Sorting the first half 
        mergeSort(R) # Sorting the second half 
  
        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
  
# Code to print the list 
def printList(arr): 
    for i in range(len(arr)):         
        print(arr[i], end =" ") 
    print() 
  
# driver code to test the above code 
if __name__ == '__main__': 
    arr = [12, 11, 13, 5, 6, 7]  
    print ("Given array is", end ="\n")  
    printList(arr) 
    mergeSort(arr) 
    print("Sorted array is: ", end ="\n") 
    printList(arr)