# Merge an array of size n into another array of size m+n

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[]).

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

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

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 ` `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*/` `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 */` `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 ` ` `  `/* 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*/` `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 */` `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 ``=` `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) ``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

 `= 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 ` `?> `

## Javascript

 ``

Output

`2 5 7 8 9 13 15 20 25 `

Time Complexity: O(m+n)
Auxiliary Space: O(1)

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

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