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# Find K such that array A can be converted into array B by adding K to a selected range [L, R]

• Last Updated : 03 Jun, 2021

Given two arrays a[] and b[] of length N consisting of unique elements, the task is to find a number K (K > 0) such that the first array can be converted into the second array by adding K to a selected range [L, R] in the array. If no such number K exists, print NA

Examples:

Input: a[] = {3, 7, 1, 4, 0, 2, 2}, b[] = {3, 7, 3, 6, 2, 2, 2}
Output:
Explanation:
Array a[] can be converted into Array b[] by adding K = 2 to range [2, 4]

Input: a[] = {3, 7, 1, 4, 0, 1, 2}, b[] = {3, 7, 3, 6, 2, 2}
Output: NA

Approach

• Create a temporary array c[] which contains the difference between the array elements, i.e.,

`ci = bi - ai`
• Then create a vector pair for all non-zero elements of the array c[n] with their index. Therefore, the vector pair will be as:

```vector<c[i], o>

where c[i] is a non zero value in c[]
and i is the index of c[i]```
• If the index value differs by 1 and the difference value is the same, then K = difference value and [L, R] = the index range.
• Hence, the array a[n] can be converted into b[n] by adding K to [a[L], a[R]].

For Example:

• Given
```a[n] = [3, 7, 1, 4, 0, 2, 2]
b[n] = [3, 7, 3, 6, 2, 2, 2]```
• So, upon creating the temporary array c[] and a vector pair:
```c[n] = [0, 0, 2, 2, 2, 0, 0]
vector pair = {{2, 2}, {2, 3}, {2, 4}}```
• As all the index values (2, 3, 4) in the vector pair differ by 1, so they are consecutive.
• And the value of the difference is the same (2).
• Hence, we can simply add that different value in the first array a[n] in the given indexes [2, 4] to convert it into a second array b[n].

• Hence, the required K value will be 2

Below is the implementation of the above approach:

## C++

 `// C++ implementation of above approach` `#include ``using` `namespace` `std;` `// Function to Check if it is possible to``// convert a given array to another array``// by adding elements to first array``bool` `checkconv(``int` `a[], ``int` `b[], ``int` `n)``{``    ``int` `c[n], flag = 0;` `    ``// Create a temporary array c[]``    ``// which contains the difference``    ``// of the array elements``    ``for` `(``int` `i = 0; i < n; i++) {` `        ``c[i] = b[i] - a[i];``    ``}` `    ``// Create a vector pair for all non zero``    ``// elements of array c[n] with there index``    ``vector > idxs;``    ``for` `(``int` `i = 0; i < n; i++) {``        ``if` `(c[i] != 0)``            ``idxs.push_back(make_pair(i, c[i]));``    ``}` `    ``// Check If the index value differs by 1``    ``// and the difference value is same``    ``for` `(``int` `i = 0; i < idxs.size() - 1; i++) {``        ``if` `(idxs[i + 1].first - idxs[i].first != 1``            ``|| idxs[i + 1].second != idxs[i].second) {``            ``flag = 1;``            ``break``;``        ``}``    ``}` `    ``return` `!flag;``}` `// Function to calculate the value of K``int` `diffofarrays(``int` `a[], ``int` `b[], ``int` `n)``{``    ``int` `c[n], ans = 0;``    ``for` `(``int` `i = 0; i < n; i++) {``        ``c[i] = b[i] - a[i];``    ``}``    ``for` `(``int` `i = 0; i < n; i++) {``        ``if` `(c[i] != 0) {``            ``ans = c[i];``            ``break``;``        ``}``    ``}` `    ``return` `ans;``}` `// Driver code``int` `main()``{``    ``int` `A[] = { 3, 7, 1, 4, 0, 2, 2 };``    ``int` `B[] = { 3, 7, 3, 6, 2, 2, 2 };``    ``int` `arr_size = ``sizeof``(A) / ``sizeof``(A[0]);` `    ``if` `(checkconv(A, B, arr_size)) {``        ``cout << diffofarrays(A, B, arr_size) << endl;``    ``}``    ``else``        ``cout << ``"NA"` `<< endl;``    ``return` `0;``}`

## Java

 `// Java implementation of above approach``import` `java.util.*;` `class` `GFG``{``    ``static` `class` `pair``    ``{``        ``int` `first, second;``        ``public` `pair(``int` `first, ``int` `second)``        ``{``            ``this``.first = first;``            ``this``.second = second;``        ``}``    ``}``    ` `// Function to Check if it is possible to``// convert a given array to another array``// by adding elements to first array``static` `boolean` `checkconv(``int` `a[], ``int` `b[], ``int` `n)``{``    ``int` `[]c = ``new` `int``[n];``    ``int` `flag = ``0``;` `    ``// Create a temporary array c[]``    ``// which contains the difference``    ``// of the array elements``    ``for` `(``int` `i = ``0``; i < n; i++)``    ``{` `        ``c[i] = b[i] - a[i];``    ``}` `    ``// Create a vector pair for all non zero``    ``// elements of array c[n] with there index``    ``Vector idxs = ``new` `Vector();``    ``for` `(``int` `i = ``0``; i < n; i++)``    ``{``        ``if` `(c[i] != ``0``)``            ``idxs.add(``new` `pair(i, c[i]));``    ``}` `    ``// Check If the index value differs by 1``    ``// and the difference value is same``    ``for` `(``int` `i = ``0``; i < idxs.size() - ``1``; i++)``    ``{``        ``if` `(idxs.get(i + ``1``).first - idxs.get(i).first != ``1``            ``|| idxs.get(i + ``1``).second != idxs.get(i).second)``        ``{``            ``flag = ``1``;``            ``break``;``        ``}``    ``}` `    ``return` `flag == ``1` `? ``false``:``true``;``}` `// Function to calculate the value of K``static` `int` `diffofarrays(``int` `a[], ``int` `b[], ``int` `n)``{``    ``int` `[]c = ``new` `int``[n];``    ``int` `ans = ``0``;``    ``for` `(``int` `i = ``0``; i < n; i++)``    ``{``        ``c[i] = b[i] - a[i];``    ``}``    ``for` `(``int` `i = ``0``; i < n; i++)``    ``{``        ``if` `(c[i] != ``0``)``        ``{``            ``ans = c[i];``            ``break``;``        ``}``    ``}``    ``return` `ans;``}` `// Driver code``public` `static` `void` `main(String[] args)``{``    ``int` `A[] = { ``3``, ``7``, ``1``, ``4``, ``0``, ``2``, ``2` `};``    ``int` `B[] = { ``3``, ``7``, ``3``, ``6``, ``2``, ``2``, ``2` `};``    ``int` `arr_size = A.length;` `    ``if` `(checkconv(A, B, arr_size))``    ``{``        ``System.out.print(diffofarrays(A, B, arr_size) +``"\n"``);``    ``}``    ``else``        ``System.out.print(``"NA"` `+``"\n"``);``}``}` `// This code is contributed by 29AjayKumar`

## Python3

 `# Python3 implementation of above approach` `# Function to Check if it is possible to``# convert a given array to another array``# by adding elements to first array``def` `checkconv(a, b, n) :` `    ``c ``=` `[``0``]``*``n; flag ``=` `0``;` `    ``# Create a temporary array c[]``    ``# which contains the difference``    ``# of the array elements``    ``for` `i ``in` `range``(n) :``        ``c[i] ``=` `b[i] ``-` `a[i];` `    ``# Create a vector pair for all non zero``    ``# elements of array c[n] with there index``    ``idxs ``=` `[];``    ``for` `i ``in` `range``(n) :``        ``if` `(c[i] !``=` `0``) :``            ``idxs.append((i, c[i]));` `    ``# Check If the index value differs by 1``    ``# and the difference value is same``    ``for` `i ``in` `range``(``len``(idxs) ``-` `1``) :``        ``if` `(idxs[i ``+` `1``][``0``] ``-` `idxs[i][``0``] !``=` `1``            ``or` `idxs[i ``+` `1``][``1``] !``=` `idxs[i][``1``]) :``            ``flag ``=` `1``;``            ``break``;` `    ``return` `not` `flag;` `# Function to calculate the value of K``def` `diffofarrays(a, b, n) :``    ``c ``=` `[``0``] ``*` `n;``    ``ans ``=` `0``;``    ` `    ``for` `i ``in` `range``(n) :``        ``c[i] ``=` `b[i] ``-` `a[i];``        ` `    ``for` `i ``in` `range``(n) :``        ``if` `(c[i] !``=` `0``) :``            ``ans ``=` `c[i];``            ``break``;``    ` `    ``return` `ans;` `# Driver code``if` `__name__ ``=``=` `"__main__"` `:` `    ``A ``=` `[ ``3``, ``7``, ``1``, ``4``, ``0``, ``2``, ``2` `];``    ``B ``=` `[ ``3``, ``7``, ``3``, ``6``, ``2``, ``2``, ``2` `];``    ``arr_size ``=` `len``(A);``    ` `    ``if` `(checkconv(A, B, arr_size)) :``        ``print``(diffofarrays(A, B, arr_size));``        ` `    ``else` `:``        ``print``(``"NA"``);` `# This code is contributed by AnkitRai01`

## C#

 `// C# implementation of above approach``using` `System;``using` `System.Collections.Generic;` `class` `GFG``{``    ``class` `pair``    ``{``        ``public` `int` `first, second;``        ``public` `pair(``int` `first, ``int` `second)``        ``{``            ``this``.first = first;``            ``this``.second = second;``        ``}``    ``}``    ` `// Function to Check if it is possible to``// convert a given array to another array``// by adding elements to first array``static` `bool` `checkconv(``int` `[]a, ``int` `[]b, ``int` `n)``{``    ``int` `[]c = ``new` `int``[n];``    ``int` `flag = 0;` `    ``// Create a temporary array c[]``    ``// which contains the difference``    ``// of the array elements``    ``for` `(``int` `i = 0; i < n; i++)``    ``{` `        ``c[i] = b[i] - a[i];``    ``}` `    ``// Create a vector pair for all non zero``    ``// elements of array c[n] with there index``    ``List idxs = ``new` `List();``    ``for` `(``int` `i = 0; i < n; i++)``    ``{``        ``if` `(c[i] != 0)``            ``idxs.Add(``new` `pair(i, c[i]));``    ``}` `    ``// Check If the index value differs by 1``    ``// and the difference value is same``    ``for` `(``int` `i = 0; i < idxs.Count - 1; i++)``    ``{``        ``if` `(idxs[i + 1].first - idxs[i].first != 1``            ``|| idxs[i + 1].second != idxs[i].second)``        ``{``            ``flag = 1;``            ``break``;``        ``}``    ``}` `    ``return` `flag == 1 ? ``false``:``true``;``}` `// Function to calculate the value of K``static` `int` `diffofarrays(``int` `[]a, ``int` `[]b, ``int` `n)``{``    ``int` `[]c = ``new` `int``[n];``    ``int` `ans = 0;``    ``for` `(``int` `i = 0; i < n; i++)``    ``{``        ``c[i] = b[i] - a[i];``    ``}``    ``for` `(``int` `i = 0; i < n; i++)``    ``{``        ``if` `(c[i] != 0)``        ``{``            ``ans = c[i];``            ``break``;``        ``}``    ``}``    ``return` `ans;``}` `// Driver code``public` `static` `void` `Main(String[] args)``{``    ``int` `[]A = { 3, 7, 1, 4, 0, 2, 2 };``    ``int` `[]B = { 3, 7, 3, 6, 2, 2, 2 };``    ``int` `arr_size = A.Length;` `    ``if` `(checkconv(A, B, arr_size))``    ``{``        ``Console.Write(diffofarrays(A, B, arr_size) +``"\n"``);``    ``}``    ``else``        ``Console.Write(``"NA"` `+``"\n"``);``}``}` `// This code is contributed by 29AjayKumar`

## Javascript

 ``
Output:
`2`

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