Collection of bit mask operation

Standard operations

Set the $i^{th}$ bit

mask |= 1 << i

Unset the $i^{th}$ bit

mask &= ~(1 << i)

Toggle the $i^{th}$ bit

mask ^= 1 << i

Check if $i^{th}$ bit is set

mask & (1 << i)

Get the lowest bit (least significant bit)

x & -x

C++ specific functions

Count bit 1s

__builtin_popcount(n)
// pop means population

Count trailing zeros

__builtin_ctz(n)
// ctz means count trailing zero

Count leading zeroes

__builtin_clz(n)
// clz means count leading zero

Check if n is power of 2

__builtin_popcount(n) == 1