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Merge an array of size n into another array of size m+n
  • Difficulty Level : Easy
  • Last Updated : 20 Jan, 2021

There are two sorted arrays. First one is of size m+n containing only m elements. Another one is of size n and contains n elements. Merge these two arrays into the first array of size m+n such that the output is sorted. 
Input: array with m+n elements (mPlusN[]). 
 

MergemPlusN

NA => Value is not filled/available in array mPlusN[]. There should be n such array blocks.
Input: array with n elements (N[]). 
 

MergeN

Output: N[] merged into mPlusN[] (Modified mPlusN[]) 
 



MergemPlusN_Res

 

Algorithm: 

Let first array be mPlusN[] and other array be N[]
1) Move m elements of mPlusN[] to end.
2) Start from nth element of mPlusN[] and 0th 
   element of N[] and merge them into mPlusN[].

Below is the implementation of the above algorithm : 

C++




// C++ program to Merge an array of
// size n into another array of size m + n
#include <bits/stdc++.h>
using namespace std;
 
/* Assuming -1 is filled for the places
   where element is not available */
#define NA -1
 
/* Function to move m elements at
   the end of array mPlusN[] */
void moveToEnd(int mPlusN[], int size)
{
   int j = size - 1;
   for (int i = size - 1; i >= 0; i--)
     if (mPlusN[i] != NA)
     {
        mPlusN[j] = mPlusN[i];
        j--;
     }
}
 
/* Merges array N[] of size n into
   array mPlusN[] of size m+n*/
int merge(int mPlusN[], int N[], int m, int n)
{
   int i = n; /* Current index of i/p part of mPlusN[]*/
   int j = 0; /* Current index of N[]*/
   int k = 0; /* Current index of output mPlusN[]*/
   while (k < (m + n))
   {
    /* Take an element from mPlusN[] if
    a) value of the picked element is smaller
       and we have not reached end of it
    b) We have reached end of N[] */
    if ((j == n)||(i < (m + n) && mPlusN[i] <= N[j]))
    {
        mPlusN[k] = mPlusN[i];
        k++;
        i++;
    }
    else // Otherwise take element from N[]
    {
       mPlusN[k] = N[j];
       k++;
       j++;
    }
   }
}
 
/* Utility that prints out an array on a line */
void printArray(int arr[], int size)
{
   for (int i = 0; i < size; i++)
   cout << arr[i] << " ";
 
   cout << endl;
}
 
/* Driver code */
int main()
{
   /* Initialize arrays */
   int mPlusN[] = {2, 8, NA, NA, NA, 13, NA, 15, 20};
   int N[] = {5, 7, 9, 25};
    
   int n = sizeof(N) / sizeof(N[0]);
   int m = sizeof(mPlusN) / sizeof(mPlusN[0]) - n;
 
   /*Move the m elements at the end of mPlusN*/
   moveToEnd(mPlusN, m + n);
 
   /*Merge N[] into mPlusN[] */
   merge(mPlusN, N, m, n);
 
   /* Print the resultant mPlusN */
   printArray(mPlusN, m+n);
 
   return 0;
}


C




// C program to Merge an array of
// size n into another array of size m + n
#include <stdio.h>
 
/* Assuming -1 is filled for
   the places where element
   is not available */
#define NA -1
 
/* Function to move m elements
   at the end of array mPlusN[]
 */
void moveToEnd(int mPlusN[], int size)
{
    int i = 0, j = size - 1;
    for (i = size - 1; i >= 0; i--)
        if (mPlusN[i] != NA) {
            mPlusN[j] = mPlusN[i];
            j--;
        }
}
 
/* Merges array N[] of size n into array mPlusN[]
   of size m+n*/
int merge(int mPlusN[], int N[], int m, int n)
{
    int i = n; /* Current index of i/p part of mPlusN[]*/
    int j = 0; /* Current index of N[]*/
    int k = 0; /* Current index of output mPlusN[]*/
    while (k < (m + n))
    {
        /* Take an element from mPlusN[] if
           a) value of the picked element is smaller and we
           have not reached end of it
           b) We have reached end of N[] */
        if ((j == n)|| (i < (m + n)
             && mPlusN[i] <= N[j]))
        {
            mPlusN[k] = mPlusN[i];
            k++;
            i++;
        }
        else // Otherwise take element from N[]
        {
            mPlusN[k] = N[j];
            k++;
            j++;
        }
    }
}
 
/* Utility that prints out an array on a line */
void printArray(int arr[], int size)
{
    int i;
    for (i = 0; i < size; i++)
        printf("%d ", arr[i]);
 
    printf("\n");
}
 
/* Driver code */
int main()
{
    /* Initialize arrays */
    int mPlusN[] = { 2, 8, NA, NA, NA, 13, NA, 15, 20 };
    int N[] = { 5, 7, 9, 25 };
    int n = sizeof(N) / sizeof(N[0]);
    int m = sizeof(mPlusN) / sizeof(mPlusN[0]) - n;
 
    /*Move the m elements at the end of mPlusN*/
    moveToEnd(mPlusN, m + n);
 
    /*Merge N[] into mPlusN[] */
    merge(mPlusN, N, m, n);
 
    /* Print the resultant mPlusN */
    printArray(mPlusN, m + n);
 
    return 0;
}


Java




// Java program to Merge an array of
// size n into another array of size m + n
 
class MergeArrays {
    /* Function to move m
       elements at the end of array
     * mPlusN[] */
    void moveToEnd(int mPlusN[], int size)
    {
        int i, j = size - 1;
        for (i = size - 1; i >= 0; i--) {
            if (mPlusN[i] != -1) {
                mPlusN[j] = mPlusN[i];
                j--;
            }
        }
    }
 
    /* Merges array N[] of
       size n into array mPlusN[]
       of size m+n*/
    void merge(int mPlusN[], int N[], int m, int n)
    {
        int i = n;
 
        /* Current index of i/p part of mPlusN[]*/
        int j = 0;
 
        /* Current index of N[]*/
        int k = 0;
 
        /* Current index of output mPlusN[]*/
        while (k < (m + n))
        {
            /* Take an element from mPlusN[] if
            a) value of the picked element is smaller and we
            have not reached end of it b) We have reached
            end of N[] */
            if ((i < (m + n) && mPlusN[i] <= N[j])
                || (j == n)) {
                mPlusN[k] = mPlusN[i];
                k++;
                i++;
            }
            else // Otherwise take element from N[]
            {
                mPlusN[k] = N[j];
                k++;
                j++;
            }
        }
    }
 
    /* Utility that prints out an array on a line */
    void printArray(int arr[], int size)
    {
        int i;
        for (i = 0; i < size; i++)
            System.out.print(arr[i] + " ");
 
        System.out.println("");
    }
 
    // Driver Code
    public static void main(String[] args)
    {
        MergeArrays mergearray = new MergeArrays();
 
        /* Initialize arrays */
        int mPlusN[] = { 2, 8, -1, -1, -1, 13, -1, 15, 20 };
        int N[] = { 5, 7, 9, 25 };
        int n = N.length;
        int m = mPlusN.length - n;
 
        /*Move the m elements at the end of mPlusN*/
        mergearray.moveToEnd(mPlusN, m + n);
 
        /*Merge N[] into mPlusN[] */
        mergearray.merge(mPlusN, N, m, n);
 
        /* Print the resultant mPlusN */
        mergearray.printArray(mPlusN, m + n);
    }
}
 
// This code has been contributed by Mayank Jaiswal


Python3




# Python program to Merge an array of
# size n into another array of size m + n
 
NA = -1
 
# Function to move m elements
# at the end of array mPlusN[]
 
 
def moveToEnd(mPlusN, size):
 
    i = 0
    j = size - 1
    for i in range(size-1, -1, -1):
        if (mPlusN[i] != NA):
 
            mPlusN[j] = mPlusN[i]
            j -= 1
 
# Merges array N[]
# of size n into array mPlusN[]
# of size m+n
 
 
def merge(mPlusN, N, m, n):
 
    i = # Current index of i/p part of mPlusN[]
    j = 0  # Current index of N[]
    k = 0  # Current index of output mPlusN[]
    while (k < (m+n)):
 
        # Take an element from mPlusN[] if
        # a) value of the picked
        # element is smaller and we have
        # not reached end of it
        # b) We have reached end of N[] */
        if ((j == n) or (i < (m+n) and mPlusN[i] <= N[j])):
 
            mPlusN[k] = mPlusN[i]
            k += 1
            i += 1
 
        else# Otherwise take element from N[]
 
            mPlusN[k] = N[j]
            k += 1
            j += 1
 
# Utility that prints
# out an array on a line
 
 
def printArray(arr, size):
 
    for i in range(size):
        print(arr[i], " ", end="")
 
    print()
 
 
# Driver function to
# test above functions
 
# Initialize arrays
mPlusN = [2, 8, NA, NA, NA, 13, NA, 15, 20]
N = [5, 7, 9, 25]
n = len(N)
 
m = len(mPlusN) - n
 
# Move the m elements
# at the end of mPlusN
moveToEnd(mPlusN, m+n)
 
# Merge N[] into mPlusN[]
merge(mPlusN, N, m, n)
 
# Print the resultant mPlusN
printArray(mPlusN, m+n)
 
# This code is contributed
# by Anant Agarwal.


C#




// C# program to Merge an array of
// size n into another array of size m + n
using System;
 
class GFG {
    /* Function to move m elements at
       the end of array mPlusN[] */
    public virtual void moveToEnd(int[] mPlusN, int size)
    {
        int i, j = size - 1;
        for (i = size - 1; i >= 0; i--)
        {
            if (mPlusN[i] != -1) {
                mPlusN[j] = mPlusN[i];
                j--;
            }
        }
    }
 
    /* Merges array N[] of size n
       into array mPlusN[] of size m+n*/
    public virtual void merge(int[] mPlusN,
                              int[] N, int m,
                              int n)
    {
        int i = n;
 
        /* Current index of i/p
           part of mPlusN[]*/
        int j = 0;
 
        /* Current index of N[]*/
        int k = 0;
 
        /* Current index of output mPlusN[]*/
        while (k < (m + n))
        {
            /* Take an element from mPlusN[] if
            a) value of the picked element is smaller
               and we have not reached end of it
            b) We have reached end of N[] */
            if ((j == n)(i < (m + n)
                && mPlusN[i] <= N[j]))
            {
                mPlusN[k] = mPlusN[i];
                k++;
                i++;
            }
            else // Otherwise take element from N[]
            {
                mPlusN[k] = N[j];
                k++;
                j++;
            }
        }
    }
 
    /* Utility that prints out
       an array on a line */
    public virtual void printArray(int[] arr, int size)
    {
        int i;
        for (i = 0; i < size; i++) {
            Console.Write(arr[i] + " ");
        }
 
        Console.WriteLine("");
    }
 
    // Driver Code
    public static void Main(string[] args)
    {
        GFG mergearray = new GFG();
 
        /* Initialize arrays */
        int[] mPlusN = new int[] { 2,  8,  -1, -1, -1,
                                   13, -1, 15, 20 };
        int[] N = new int[] { 5, 7, 9, 25 };
        int n = N.Length;
        int m = mPlusN.Length - n;
 
        /*Move the m elements at the
          end of mPlusN*/
        mergearray.moveToEnd(mPlusN, m + n);
 
        /*Merge N[] into mPlusN[] */
        mergearray.merge(mPlusN, N, m, n);
 
        /* Print the resultant mPlusN */
        mergearray.printArray(mPlusN, m + n);
    }
}
 
// This code is contributed by Shrikant13


PHP




<?php
// PHP program to Merge an array
// of size n into another array
// of size m + n
 
/* Assuming -1 is filled for
the places where element is
not available */
$NA = -1;
 
/* Function to move m elements
at the end of array mPlusN[] */
function moveToEnd(&$mPlusN, $size)
{
    global $NA;
    $j = $size - 1;
    for ($i = $size - 1; $i >= 0; $i--)
        if ($mPlusN[$i] != $NA)
        {
            $mPlusN[$j] = $mPlusN[$i];
            $j--;
        }
}
 
/* Merges array N[] of size n
into array mPlusN[] of size m+n*/
function merge(&$mPlusN, &$N, $m, $n)
{
    $i = $n; /* Current index of i/p
                part of mPlusN[]*/
    $j = 0;  /* Current index of N[]*/
    $k = 0;  /* Current index of
                output mPlusN[]*/
    while ($k < ($m + $n))
    {
        /* Take an element from mPlusN[] if
        a) value of the picked element
           is smaller and we have not
           reached end of it
        b) We have reached end of N[] */
        if (($j == $n) || ($i < ($m + $n) &&
             $mPlusN[$i] <= $N[$j]))
        {
            $mPlusN[$k] = $mPlusN[$i];
            $k++;
            $i++;
        }
        else // Otherwise take element from N[]
        {
            $mPlusN[$k] = $N[$j];
            $k++;
            $j++;
        }
}
}
 
/* Utility that prints out
   an array on a line */
function printArray(&$arr, $size)
{
    for ($i = 0; $i < $size; $i++)
    echo $arr[$i] . " ";
     
    echo "\n";
}
 
// Driver Code
 
/* Initialize arrays */
$mPlusN = array(2, 8, $NA, $NA, $NA,
                13, $NA, 15, 20);
$N = array(5, 7, 9, 25);
     
$n = sizeof($N);
$m = sizeof($mPlusN) - $n;
 
/* Move the m elements
   at the end of mPlusN*/
moveToEnd($mPlusN, $m + $n);
 
/* Merge N[] into mPlusN[] */
merge($mPlusN, $N, $m, $n);
 
/* Print the resultant mPlusN */
printArray($mPlusN, $m+$n);
 
// This code is contributed
// by ChitraNayal
?>


Output

2 5 7 8 9 13 15 20 25 

Time Complexity: O(m+n)

Please write comment if you find any bug in the above program or a better way to solve the same problem.

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