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Evil Number
• Difficulty Level : Basic
• Last Updated : 29 Apr, 2021

An evil number is a non-negative number that has an even number of 1s in its binary expansion. (Binary Expansion – is representation of a number in the binary numeral system or base-2 numeral system which represents numeric values using two different symbols: typically 0 (zero) and 1 (one)).

Odious Numbers: Numbers that are not Evil are called Odious Numbers. Given a number, the task is to check if it is Evil Number or Odious Numbers.

Examples :

```Input : 3
Output : Evil Number
Explanation: Binary expansion of 3 is 11,
the number of 1s in this is 2 i.e even.

Input : 16
Output : Odious Number(not an evil number)
Explanation: Binary expansion of 16 = 10000,
having number of 1s =1 i.e odd.

Input : 23
Output : Evil Number
Explanation: Binary expansion of 23 is 10111,
the number of 1s in this is 4 i.e even. ```

## C++

 `// C/C++ program to check if a number is``// Evil number or Odious Number``#include ``using` `namespace` `std;``#include ` `// returns number of 1s from the binary number``int` `count_one(``int` `n)``{``    ``int` `c_one = 0;``    ``while` `(n != 0) {``        ``int` `rem = n % 10;` `        ``// counting 1s``        ``if` `(rem == 1)``            ``c_one = c_one + 1;``        ``n = n / 10;``    ``}``    ``return` `c_one;``}` `// Check if number is evil or not``int` `checkEvil(``int` `n)``{``    ``int` `i = 0, bin = 0, n_one = 0;` `    ``// converting n to binary form``    ``while` `(n != 0) {``        ``// calculating remainder``        ``int` `r = n % 2;` `        ``// storing the remainders in binary``        ``// form as a number``        ``bin = bin + r * (``int``)(``pow``(10, i));``        ``n = n / 2;``    ``}` `    ``// Calling the count_one function to count``    ``// and return number of 1s in bin``    ``n_one = count_one(bin);``    ``if` `(n_one % 2 == 0)``        ``return` `1;``    ``else``        ``return` `0;``}` `// Driver Code``int` `main(``void``)``{``    ``int` `i, check, num;``    ``num = 32;``    ``check = checkEvil(num);``    ``if` `(check == 1)``        ``cout << num << ``" is Evil Number\n"``;``    ``else``        ``cout << num << ``" is Odious Number\n"``;``    ``return` `0;``}` `// This code is contributed by Nikita Tiwari.`

## Java

 `// Java program to check if a number is``// Evil number or Odious Number` `class` `GFG {``    ``// returns number of 1s from the binary number``    ``static` `int` `count_one(``int` `n)``    ``{``        ``int` `c_one = ``0``;``        ``while` `(n != ``0``) {``            ``int` `rem = n % ``10``;` `            ``// counting 1s``            ``if` `(rem == ``1``)``                ``c_one = c_one + ``1``;``            ``n = n / ``10``;``        ``}``        ``return` `c_one;``    ``}` `    ``// Check if number is evil or not``    ``static` `int` `checkEvil(``int` `n)``    ``{``        ``int` `i = ``0``, bin = ``0``, n_one = ``0``;` `        ``// converting n to binary form``        ``while` `(n != ``0``) {``            ``// calculating remainder``            ``int` `r = n % ``2``;` `            ``// storing the remainders in binary``            ``// form as a number``            ``bin = bin + r * (``int``)(Math.pow(``10``, i));``            ``n = n / ``2``;``        ``}` `        ``// Calling the count_one function to count``        ``// and return number of 1s in bin``        ``n_one = count_one(bin);``        ``if` `(n_one % ``2` `== ``0``)``            ``return` `1``;``        ``else``            ``return` `0``;``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``int` `i, check, num;``        ``num = ``32``;``        ``check = checkEvil(num);``        ``if` `(check == ``1``)``            ``System.out.println(num + ``" is Evil Number"``);``        ``else``            ``System.out.println(num + ``" is Odious Number"``);``    ``}``}` `/* This code is contributed by Mr. Somesh Awasthi */`

## Python

 `# Python program to check if a number is``# Evil number or Odious number` `# returns number of 1s from the binary number``def` `count_one(n):``    ``c_one ``=` `0``    ``while` `n !``=` `0``:``        ``rem ``=` `n ``%` `10``        ` `        ``# Counting 1s``        ``if` `rem ``=``=` `1``:``            ``c_one ``=` `c_one ``+` `1``        ``n ``=` `n ``/` `10``        ` `    ``return` `c_one` `# Check if nnumber is evil or not``def` `checkEvil(n):``    ``i ``=` `0``    ``binary ``=` `0``    ` `    ``# Converting n to binary form``    ``while` `n !``=` `0``:``        ``r ``=` `n ``%` `2``        ``# Calculating Remainder``        ``# Storing the remainders in binary``        ``# form as a number``        ``binary ``=` `binary ``+` `r``*``(``int``(``10``*``*``i))``        ``n ``=` `n ``/` `2``        ` `    ``# Calling the count_one function to count``    ``# and return number of 1s in bin``    ``n_one ``=` `count_one(binary)``    ``if` `n_one ``%` `2` `=``=` `0``:``        ``return` `True``    ``return` `False``    ` `# Driver Code``num ``=` `32``check ``=` `checkEvil(num)``if` `check:``    ``print` `num, ``"is Evil Nummber"``else``:``    ``print` `num, ``"is Odious Number"`       `        ` `# Contributed by Harshit Agrawal       `

## C#

 `// C# program to check if a number is``// Evil number or Odious Number``using` `System;` `class` `GFG {` `    ``// Returns number of 1s from``    ``// the binary number``    ``static` `int` `count_one(``int` `n)``    ``{``        ``int` `c_one = 0;``        ``while` `(n != 0) {``            ``int` `rem = n % 10;` `            ``// counting 1s``            ``if` `(rem == 1)``                ``c_one = c_one + 1;``            ``n = n / 10;``        ``}``        ``return` `c_one;``    ``}` `    ``// Check if number is evil or not``    ``static` `int` `checkEvil(``int` `n)``    ``{``        ``int` `i = 0, bin = 0, n_one = 0;` `        ``// converting n to binary form``        ``while` `(n != 0) {``            ``// calculating remainder``            ``int` `r = n % 2;` `            ``// storing the remainders in``            ``// binary form as a number``            ``bin = bin + r * (``int``)(Math.Pow(10, i));``            ``n = n / 2;``        ``}` `        ``// Calling the count_one function to count``        ``// and return number of 1s in bin``        ``n_one = count_one(bin);``        ``if` `(n_one % 2 == 0)``            ``return` `1;``        ``else``            ``return` `0;``    ``}` `    ``// Driver Code``    ``public` `static` `void` `Main(String[] args)``    ``{``        ``int` `check, num;``        ``num = 32;``        ``check = checkEvil(num);``        ``if` `(check == 1)``            ``Console.WriteLine(num + ``" is Evil Number"``);``        ``else``            ``Console.WriteLine(num + ``" is Odious Number"``);``    ``}``}` `// This code is contributed by vt_m.`

## PHP

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## Javascript

 ``

Output :

`32 is Odius Number`

This article is contributed by Nikita Tiwari. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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