Re: [math-fun] Bit puzzle

Cute. "32-bit" is completely unnecessary. def f(x,n) : return x^(x>>n); def g(x,n) : while x>>n : x ^= x>>n; n*=2; return x; On 30-Aug-13 20:08, quad wrote:

Here is a little puzzle. I encourage not spelunking around for the answer on the Internet. ;)

Given a 32-bit unsigned integer x, and a positive integer n, let

a = XOR(x, RIGHTSHIFT(x, n))

or in C syntax

a = x ^ (x >> n)

find, if one exists, a function f such that f(a) = x. In other words, invert the operation on x, or show otherwise.

Cheers,

Robert

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