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# Find a value whose XOR with given number is maximum

• Difficulty Level : Basic
• Last Updated : 28 Apr, 2021

Given a value X, the task is to find the number Y which will give maximum value possible when XOR with X.
(Assume X to be 8 bits) Maximum possible value of X and Y is 255.
Examples:

```Input:  X = 2
Output: 253
Binary Representation of X = 00000010
Binary Representation of Y = 11111101
Maximum XOR value: 11111111

Input:  X = 200
Output: 55```

Approach: In order to ensure the maximum value of XOR, we need to set all those bits ON which are OFF in X. So for that, Y should have all bits ON which are OFF in X and OFF which are ON in X as (0^1 = 1 and 1^0 = 1). So Y should be the 1’s complement representation of X.
Below is the implementation of the above approach:

## C++

 `// C++ implementation of the above approach``#include ``using` `namespace` `std;` `// Function To Calculate Answer``int` `calculate(``int` `X)``{``    ``// Find number of bits in the given integer``    ``int` `number_of_bits = 8;` `    ``// XOR the given integer with poe(2,``    ``// number_of_bits-1 and print the result``    ``return` `((1 << number_of_bits) - 1) ^ X;``}` `// Driver Code``int` `main()``{``    ``int` `X = 4;` `    ``cout << ``"Required Number is : "``         ``<< calculate(X) << endl;` `    ``return` `0;``}`

## Java

 `// Java implementation of the above approach` `import` `java.io.*;` `class` `GFG {``    ` `// Function To Calculate Answer``static` `int` `calculate(``int` `X)``{``    ``// Find number of bits in the given integer``    ``int` `number_of_bits = ``8``;` `    ``// XOR the given integer with poe(2,``    ``// number_of_bits-1 and print the result``    ``return` `((``1` `<< number_of_bits) - ``1``) ^ X;``}` `// Driver Code`  `    ``public` `static` `void` `main (String[] args) {``        ``int` `X = ``4``;` `    ``System.out.println( ``"Required Number is : "``        ``+calculate(X));``    ``}``}``// This code is contributed by shs..`

## Python3

 `# Python3 implementation of the above approach` `# Function To Calculate Answer``def` `calculate(X):`` ` `    ``# Find number of bits in the given integer``    ``number_of_bits ``=` `8``  ` `    ``# XOR the given integer with poe(2,``    ``# number_of_bits-1 and print the result``    ``return` `((``1` `<< number_of_bits) ``-` `1``) ^ X``  ` `# Driver Code``if` `__name__ ``=``=` `"__main__"``:`` ` `    ``X ``=` `4``    ``print``(``"Required Number is:"``, calculate(X))``  ` `# This code is contributed by Rituraj Jain`

## C#

 `// C# implementation of the above approach``using` `System;` `class` `GFG``{``    ` `// Function To Calculate Answer``static` `int` `calculate(``int` `X)``{``    ``// Find number of bits in``    ``// the given integer``    ``int` `number_of_bits = 8;` `    ``// XOR the given integer with poe(2,``    ``// number_of_bits-1 and print the result``    ``return` `((1 << number_of_bits) - 1) ^ X;``}` `// Driver Code``public` `static` `void` `Main ()``{``    ``int` `X = 4;` `    ``Console.WriteLine(``"Required Number is : "` `+``                                 ``calculate(X));``}``}` `// This code is contributed by shs..`

## PHP

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## Javascript

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Output:
`Required Number is : 251`

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