# A Boolean Array Puzzle

Input: A array arr[] of two elements having value 0 and 1

Output: Make both elements 0.

Specifications: Following are the specifications to follow.
1) It is guaranteed that one element is 0 but we do not know its position.
2) We can’t say about another element it can be 0 or 1.
3) We can only complement array elements, no other operation like and, or, multi, division, …. etc.
4) We can’t use if, else and loop constructs.
5) Obviously, we can’t directly assign 0 to array elements.

There are several ways we can do it as we are sure that always one Zero is there. Thanks to devendraiiit for suggesting following 3 methods.

Method 1

 `void` `changeToZero(``int` `a) ` `{ ` `   ``a[ a ] = a[ !a ]; ` `} ` ` `  `int` `main() ` `{ ` `   ``int` `a[] = {1, 0}; ` `   ``changeToZero(a); ` ` `  `   ``printf``(````" arr = %d "````, a); ` `   ``printf``(``" arr = %d "``, a); ` `   ``getchar``(); ` `   ``return` `0; ` `} `

Method 2

 `void` `changeToZero(``int` `a) ` `{ ` `    ``a[ !a ] = a[ !a ] ` `} `

Method 3
This method doesn’t even need complement.

 `void` `changeToZero(``int` `a) ` `{ ` `    ``a[ a ] = a[ a ] ` `} `

Method 4
Thanks to purvi for suggesting this method.

 `void` `changeToZero(``int` `a) ` `{ ` `  ``a = a[a]; ` `  ``a = a; ` `} `

There may be many more methods.

Please write comments if you find the above codes incorrect, or find other ways to solve the same problem.

## tags:

Bit Magic Bit Magic