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# Sorted merge in one array

• Difficulty Level : Medium
• Last Updated : 21 Jun, 2021

Given two sorted arrays, A and B, where A has a large enough buffer at the end to hold B.
Merge B into A in sorted order.
Examples:

```Input : a[] = {10, 12, 13, 14, 18, NA, NA, NA, NA, NA}
b[] = {16, 17, 19, 20, 22};;
Output : a[] = {10, 12, 13, 14, 16, 17, 18, 19, 20, 22}```

One way is to merge the two arrays by inserting the smaller elements to front of A, but the issue with this approach is that we have to shift every element to right after every insertion.
So, instead from comparing which one is smaller element, we can compare which one is larger and then inserting that element to end of A.
Below is the solution for above approach.

## C++

 `// Merging b[] into a[]``#include ``using` `namespace` `std;``#define NA -1` `void` `sortedMerge(``int` `a[], ``int` `b[], ``int` `n, ``int` `m) {``  ``int` `i = n - 1;``  ``int` `j = m - 1;` `  ``int` `lastIndex = n + m - 1;` `  ``/* Merge a and b, starting from last element``     ``in each */``  ``while` `(j >= 0) {` `    ``/* End of a is greater than end of b */``    ``if` `(i >= 0 && a[i] > b[j]) {``      ``a[lastIndex] = a[i]; ``// Copy Element``      ``i--;``    ``} ``else` `{``      ``a[lastIndex] = b[j]; ``// Copy Element``      ``j--;``    ``}``    ``lastIndex--; ``// Move indices``  ``}``}` `/* Helper function to print the array */``void` `printArray(``int` `*arr, ``int` `n) {``  ``cout << ``"Array A after merging B in sorted"``        ``" order : "` `<< endl;``  ``for` `(``int` `i = 0; i < n; i++)``    ``cout << arr[i] << ``" "``;``}` `int` `main() {``  ``int` `a[] = {10, 12, 13, 14, 18, NA, NA, NA, NA, NA};``  ``int` `n = 5;``  ``int` `size_a = 10;``  ``int` `b[] = {16, 17, 19, 20, 22};``  ``int` `m = 5;``  ``sortedMerge(a, b, n, m);``  ``printArray(a, size_a);``  ``return` `0;``}`

## Java

 `// Java  program to merge B``// into A in sorted order.``import` `java.io.*;` `class` `GFG``{``    ``static` `int` `NA =-``1``;``    ``static` `void` `sortedMerge(``int` `a[], ``int` `b[], ``int` `n, ``int` `m)``    ``{``        ``int` `i = n - ``1``;``        ``int` `j = m - ``1``;``        ` `        ``int` `lastIndex = n + m - ``1``;``        ` `        ``// Merge a and b, starting``        ``// from last element in each``        ``while` `(j >= ``0``)``        ``{``        ` `            ``/* End of a is greater than end of b */``            ``if` `(i >= ``0` `&& a[i] > b[j])``            ``{``                ``// Copy Element``                ``a[lastIndex] = a[i];``                ``i--;``            ``} ``else``            ``{ ``                ``// Copy Element``                ``a[lastIndex] = b[j];``                ``j--;``            ``}``            ``// Move indices``            ``lastIndex--;``        ``}``    ``}``    ` `    ``// Helper function to print the array``    ``static` `void` `printArray(``int` `arr[], ``int` `n)``    ``{``        ``System.out.println ( ``"Array A after merging B in sorted order : "` `) ;``        ``for` `(``int` `i = ``0``; i < n; i++)``            ``System.out.print(arr[i] +``" "``);``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `main (String[] args)``    ``{``        ``int` `a[] = {``10``, ``12``, ``13``, ``14``, ``18``, NA, NA, NA, NA, NA};``        ``int` `n = ``5``;``        ``int` `size_a = ``10``;``        ``int` `b[] = {``16``, ``17``, ``19``, ``20``, ``22``};``        ``int` `m = ``5``;``        ``sortedMerge(a, b, n, m);``        ``printArray(a, size_a);``    ``}``}` `// This code is contributed by vt_m.`

## Python3

 `# Python3 program to merge B``# into A in sorted order.` `NA ``=` `-``1` `# Merging b[] into a[]``def` `sortedMerge(a, b, n, m):` `    ``i ``=` `n ``-` `1``    ``j ``=` `m ``-` `1``    ` `    ``lastIndex ``=` `n ``+` `m ``-` `1``    ` `    ``# Merge a and b, starting from last``    ``# element in each``    ``while` `(j >``=` `0``) :``    ` `        ``# End of a is greater than end``        ``# of b``        ``if` `(i >``=` `0` `and` `a[i] > b[j]):``            ` `            ``# Copy Element``            ``a[lastIndex] ``=` `a[i]``            ``i ``-``=` `1``        ``else``:``            ` `             ``# Copy Element``            ``a[lastIndex] ``=` `b[j]``            ``j ``-``=` `1``        ` `        ``# Move indices``        ``lastIndex``-``=` `1` `# Helper function to print``# the array``def` `printArray(arr, n):` `    ``print``(``"Array A after merging B in sorted order : "``)` `    ``for` `i ``in` `range``(``0``, n):``        ``print``(arr[i], end ``=``" "``)` `size_a ``=` `10` `a ``=` `[``10``, ``12``, ``13``, ``14``, ``18``, NA, NA, NA, NA, NA]``n ``=` `5` `b ``=` `[``16``, ``17``, ``19``, ``20``, ``22``]``m ``=` `5` `sortedMerge(a, b, n, m)``printArray(a, size_a)` `# This code is contributed by``# Smitha Dinesh Semwal`

## C#

 `// C# program to merge B into A in``// sorted order.``using` `System;` `class` `GFG {``    ` `    ``static` `int` `NA =-1;``    ``static` `void` `sortedMerge(``int` `[]a, ``int` `[]b,``                                 ``int` `n, ``int` `m)``    ``{``        ``int` `i = n - 1;``        ``int` `j = m - 1;``        ` `        ``int` `lastIndex = n + m - 1;``        ` `        ``// Merge a and b, starting``        ``// from last element in each``        ``while` `(j >= 0)``        ``{``        ` `            ``/* End of a is greater than``            ``end of b */``            ``if` `(i >= 0 && a[i] > b[j])``            ``{``                ` `                ``// Copy Element``                ``a[lastIndex] = a[i];``                ``i--;``            ``}``            ` `            ``else``            ``{``                ` `                ``// Copy Element``                ``a[lastIndex] = b[j];``                ``j--;``            ``}``            ` `            ``// Move indices``            ``lastIndex--;``        ``}``    ``}``    ` `    ``// Helper function to print the array``    ``static` `void` `printArray(``int` `[]arr, ``int` `n)``    ``{``        ` `        ``Console.WriteLine ( ``"Array A after "``        ``+ ``"merging B in sorted order : "` `) ;``        ` `        ``for` `(``int` `i = 0; i < n; i++)``            ``Console.Write(arr[i] +``" "``);``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `Main ()``    ``{``        ``int` `[]a = {10, 12, 13, 14, 18, NA,``                           ``NA, NA, NA, NA};``        ``int` `n = 5;``        ``int` `size_a = 10;``        ``int` `[]b = {16, 17, 19, 20, 22};``        ``int` `m = 5;``        ` `        ``sortedMerge(a, b, n, m);``        ` `        ``printArray(a, size_a);``    ``}``}` `// This code is contributed by vt_m.`

## PHP

 `= 0)``    ``{``    ` `        ``/* End of a is greater than end of b */``        ``if` `(``\$i` `>= 0 && ``\$a``[``\$i``] > ``\$b``[``\$j``])``        ``{``            ``\$a``[``\$lastIndex``] = ``\$a``[``\$i``]; ``// Copy Element``            ``\$i``--;``        ``}``        ``else``        ``{``            ``\$a``[``\$lastIndex``] = ``\$b``[``\$j``]; ``// Copy Element``            ``\$j``--;``        ``}``        ``\$lastIndex``--; ``// Move indices``    ``}``    ``return` `\$a``;``}` `/* Helper function to print the array */``function` `printArray(``\$arr``, ``\$n``)``{``    ``echo` `"Array A after merging B in sorted"``;``        ``echo` `" order : \n"``;``    ``for` `(``\$i` `= 0; ``\$i` `< ``\$n``; ``\$i``++)``        ``echo` `\$arr``[``\$i``] . ``" "``;``}` `// Driver Code``\$a` `= ``array``(10, 12, 13, 14, 18,``          ``-1, -1, -1, -1, -1);``\$n` `= 5;``\$size_a` `= 10;` `\$b` `= ``array``(16, 17, 19, 20, 22);``\$m` `= 5;``\$c` `= sortedMerge(``\$a``, ``\$b``, ``\$n``, ``\$m``);``printArray(``\$c``, ``\$size_a``);` `// This code is contributed by Rajput-Ji.``?>`

## Javascript

 ``
Output:
```Array A after merging B in sorted order :
10 12 13 14 16 17 18 19 20 22```

Time complexity is O(m+n).

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