Merging elements of two different arrays alternatively in third array

Given two arrays arr1[] and arr2[], we need to combine two arrays in such a way that the combined array has alternate elements of both. If one array has extra element, then these elements are appended at the end of the combined array.

Input : arr1[] = {1, 2, 3, 4, 5, 6}
           arr2[] = {11, 22, 33, 44}
Output: {1, 11, 2, 22, 3, 33, 4, 44, 5, 6}

Input : arr1[] = {1, 2, 3, 4, 5, 6, 7, 8} 
            arr2[] = {11, 22, 33, 44}
Output: {1, 11, 2, 22, 3, 33, 4, 44, 5, 6, 7, 8}

We traverse both given arrays and one by one put their elements into combined array. After one of the arrays is exhausted, we put remaining elements of other array. 

Implementation:

C

// C program to merge two sorted arrays/
#include <stdio.h>

// Alternatively merge arr1[0..n1-1] and arr2[0..n2-1]
// into arr3[0..n1+n2-1]
void alternateMerge(int arr1[], int arr2[], int n1, int n2,
                    int arr3[])
{
    int i = 0, j = 0, k = 0;

    // Traverse both array
    while (i < n1 && j < n2) {
        arr3[k++] = arr1[i++];
        arr3[k++] = arr2[j++];
    }

    // Store remaining elements of first array
    while (i < n1)
        arr3[k++] = arr1[i++];

    // Store remaining elements of second array
    while (j < n2)
        arr3[k++] = arr2[j++];
}

// Driver code
int main()
{
    int arr1[] = { 1, 3, 5, 7, 9, 11 };
    int n1 = sizeof(arr1) / sizeof(arr1[0]);

    int arr2[] = { 2, 4, 6, 8 };
    int n2 = sizeof(arr2) / sizeof(arr2[0]);

    int arr3[n1 + n2];
    alternateMerge(arr1, arr2, n1, n2, arr3);

    printf("Array after merging\n");
    for (int i = 0; i < n1 + n2; i++)
        printf("%d ",arr3[i]);

    return 0;
}

C++

// C++ program to merge two sorted arrays/
#include <iostream>
using namespace std;

// Alternatively merge arr1[0..n1-1] and arr2[0..n2-1]
// into arr3[0..n1+n2-1]
void alternateMerge(int arr1[], int arr2[], int n1, int n2,
                    int arr3[])
{
    int i = 0, j = 0, k = 0;

    // Traverse both array
    while (i < n1 && j < n2) {
        arr3[k++] = arr1[i++];
        arr3[k++] = arr2[j++];
    }

    // Store remaining elements of first array
    while (i < n1)
        arr3[k++] = arr1[i++];

    // Store remaining elements of second array
    while (j < n2)
        arr3[k++] = arr2[j++];
}

// Driver code
int main()
{
    int arr1[] = { 1, 3, 5, 7, 9, 11 };
    int n1 = sizeof(arr1) / sizeof(arr1[0]);

    int arr2[] = { 2, 4, 6, 8 };
    int n2 = sizeof(arr2) / sizeof(arr2[0]);

    int arr3[n1 + n2];
    alternateMerge(arr1, arr2, n1, n2, arr3);

    cout << "Array after merging" << endl;
    for (int i = 0; i < n1 + n2; i++)
        cout << arr3[i] << " ";

    return 0;
}

Java

// Java program to merge two sorted arrays
import java.io.*;

class GFG {

    // Alternatively merge arr1[0..n1-1] and
    // arr2[0..n2-1] into arr3[0..n1+n2-1]
    static void alternateMerge(int arr1[], int arr2[],
                               int n1, int n2, int arr3[])
    {
        int i = 0, j = 0, k = 0;

        // Traverse both array
        while (i < n1 && j < n2) {
            arr3[k++] = arr1[i++];
            arr3[k++] = arr2[j++];
        }

        // Store remaining elements of first array
        while (i < n1)
            arr3[k++] = arr1[i++];

        // Store remaining elements of second array
        while (j < n2)
            arr3[k++] = arr2[j++];
    }

    // Driver code
    public static void main(String args[])
    {
        int arr1[] = { 1, 3, 5, 7, 9, 11 };
        int n1 = arr1.length;

        int arr2[] = { 2, 4, 6, 8 };
        int n2 = arr2.length;

        int arr3[] = new int[n1 + n2];
        alternateMerge(arr1, arr2, n1, n2, arr3);

        System.out.println("Array after merging");
        for (int i = 0; i < n1 + n2; i++)
            System.out.print(arr3[i] + " ");
    }
}

// This code is contributed
// by Nikita Tiwari.

Python3

# Python3 program to merge two sorted arrays/

# Alternatively merge arr1[0..n1-1] and
# arr2[0..n2-1] into arr3[0..n1 + n2-1]


def alternateMerge(arr1, arr2, n1, n2, arr3):
    i = 0
    j = 0
    k = 0

    # Traverse both array
    while (i < n1 and j < n2):
        arr3[k] = arr1[i]
        i += 1
        k += 1

        arr3[k] = arr2[j]
        j += 1
        k += 1

    # Store remaining elements of first array
    while (i < n1):
        arr3[k] = arr1[i]
        i += 1
        k += 1

    # Store remaining elements of second array
    while (j < n2):
        arr3[k] = arr2[j]
        k += 1
        j += 1


# Driver code
arr1 = [1, 3, 5, 7, 9, 11]
n1 = len(arr1)

arr2 = [2, 4, 6, 8]
n2 = len(arr2)

arr3 = [0] * (n1 + n2)
alternateMerge(arr1, arr2, n1, n2, arr3)

print("Array after merging")
for i in range(0, (n1 + n2)):
    print(arr3[i], end=" ")

# This code is contributed by Nikita Tiwari.

C#

// C# program to merge two sorted arrays
using System;

class GFG {

    // Alternatively merge arr1[0..n1-1]
    // and arr2[0..n2-1] into arr3[0..n1+n2-1]
    static void alternateMerge(int[] arr1, int[] arr2,
                               int n1, int n2, int[] arr3)
    {
        int i = 0, j = 0, k = 0;

        // Traverse both array
        while (i < n1 && j < n2) {
            arr3[k++] = arr1[i++];
            arr3[k++] = arr2[j++];
        }

        // Store remaining elements of first array
        while (i < n1)
            arr3[k++] = arr1[i++];

        // Store remaining elements of second array
        while (j < n2)
            arr3[k++] = arr2[j++];
    }

    // Driver code
    public static void Main()
    {
        int[] arr1 = new int[] { 1, 3, 5, 7, 9, 11 };
        int n1 = arr1.Length;

        int[] arr2 = new int[] { 2, 4, 6, 8 };
        int n2 = arr2.Length;

        int[] arr3 = new int[n1 + n2];
        alternateMerge(arr1, arr2, n1, n2, arr3);

        Console.WriteLine("Array after merging");
        for (int i = 0; i < n1 + n2; i++)
            Console.Write(arr3[i] + " ");
    }
}

// This code is contributed by Sam007.

PHP

<?php
// PHP program to merge two
// sorted arrays

// Alternatively merge arr1[0..n1-1]
// and arr2[0..n2-1] into
// arr3[0..n1+n2-1]
function alternateMerge($arr1, $arr2,
                        $n1, $n2)
{
    $i = 0;
    $j = 0;
    $k = 0;
    $arr3 = array();

    // Traverse both array
    while ($i < $n1 && $j < $n2)
    {
        $arr3[$k++] = $arr1[$i++];
        $arr3[$k++] = $arr2[$j++];
    }

    // Store remaining elements
    // of first array
    while ($i < $n1)
        $arr3[$k++] = $arr1[$i++];

    // Store remaining elements
    // of second array
    while($j < $n2)
        $arr3[$k++] = $arr2[$j++];

    echo "Array after merging"."\n";
    for ($i = 0; $i < ($n1 + $n2); $i++)
        echo $arr3[$i] ." ";

}

    // Driver Code
    $arr1 = array(1, 3, 5, 7, 9, 11);
    $n1 = count($arr1);

    $arr2 = array(2, 4, 6, 8);
    $n2 = count($arr2);
    alternateMerge($arr1, $arr2, $n1, $n2);

// This code is contributed by Sam007
?>

Javascript

<script>

// Javascript program to merge two sorted arrays/

// Alternatively merge arr1[0..n1-1] and arr2[0..n2-1]
// into arr3[0..n1+n2-1]
function alternateMerge(arr1, arr2, n1,
                    n2, arr3)
{
    let i = 0, j = 0, k = 0;

    // Traverse both array
    while (i<n1 && j <n2)
    {
        arr3[k++] = arr1[i++];
        arr3[k++] = arr2[j++];
    }

    // Store remaining elements of first array
    while (i < n1)
        arr3[k++] = arr1[i++];

    // Store remaining elements of second array
    while (j < n2)
        arr3[k++] = arr2[j++];
}

// Driver code

    let arr1 = [1, 3, 5, 7, 9, 11];
    let n1 = arr1.length;

    let arr2 = [2, 4, 6, 8];
    let n2 = arr2.length;

    let arr3 = new Array(n1+n2);
    alternateMerge(arr1, arr2, n1, n2, arr3);

    document.write("Array after merging" + "<br>");
    for (let i=0; i < n1+n2; i++)
        document.write(arr3[i] + " ");

// This code is contributed by Mayank Tyagi

</script>

Output

Array after merging
1 2 3 4 5 6 7 8 9 11 

Time Complexity: O(n1 + n2), where n1 and n2 are the sizes of the given two arrays.
Auxiliary Space: O(n1 + n2)