The collection of useful bit operations for speed and sanity purposes

bit_shortcuts.cpp

// Number of leading zeroes: builtin_clz(x)
// Number of trailing zeroes : builtin_ctz(x)
// Number of 1-bits: __builtin_popcount(x) 
// The parity (even or odd) of the number of ones: __builtin_parity(x)

// a * 2^n
constexpr int multiplyByPowerOf2(int a, int n) {
  return a << n;
}

// a / 2^n
constexpr int divideByPowerOf2(int a, int n) {
  return a >> n;
}

// quickest way to swap to numbers
constexpr void xorswap(int& a, int& b) {
  a ^= b;
  b ^= a;
  a ^= b;
}

// Highest power of 2 that divides a given number
constexpr int highestPowerof2(int n) {
  return n & (~(n - 1));
}

constexpr bool isPowerOfTwo(int x)
{
   // First x in the below expression is
   // for  the case when x is 0
   return x && (!(x & (x - 1)))
}