CODEWITHSUNDEEP
language-agnosticbit-manipulation
roulette01
roulette01

Reputation: 2462

What does (x & (x >> 1) == 0) check for?

I saw this statement in a large code base, and I don't know what this check using bit manipulation is for. Is this some standard trick in bit manipulation? If so, what is it looking for?

I know that in binary, x >> 1 shifts all the bits of x to the right 1 place, so anding that with x will guarantee the largest set bit of x becomes zero. But I just don't understand the purpose of this check.

Upvotes: 2

Views: 472

Answers (1)

user555045
user555045

Reputation: 64904

(x & (x >> 1)) == 0 (extra parentheses added for safety) checks if there are adjacent set bits in x, and evaluates to true if there aren't.

For example:

10101010 -> true
00010000 -> true
00000011 -> false
10100110 -> false

Upvotes: 3

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