# Find a value whose XOR with given number is maximum

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 = 2Output:253 Binary Representation of X = 00000010 Binary Representation of Y = 11111101 Maximum XOR value: 11111111Input:X = 200Output: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 <bits/stdc++.h>` `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

`<?php` `// PHP implementation of the` `// above approach` `// Function To Calculate Answer` `function` `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` `$X` `= 4;` `echo` `"Required Number is : "` `.` ` ` `calculate(` `$X` `) . ` `"\n"` `;` `// This code is contributed` `// by Akanksha Rai` `?>` |

## Javascript

`<script>` `// Javascript implementation of the above approach` `// Function To Calculate Answer` `function` `calculate(X)` `{` ` ` `// Find number of bits in the given integer` ` ` `let 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` ` ` `let X = 4;` ` ` `document.write(` `"Required Number is : "` ` ` `+ calculate(X) + ` `"<br>"` `);` `</script>` |

**Output:**

Required Number is : 251

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