190. Reverse Bits

Reverse the bits of a 32-bit unsigned integer n and return the result as an unsigned integer.

Swap the two 16-bit halves, then the 8-bit halves inside each, then 4, 2 and 1. Five mask-and-shift steps reverse all 32 bits.

1function reverseBits(n: number): number {
2  n = (n >>> 16) | (n << 16);
3  n = ((n & 0xff00ff00) >>> 8) | ((n & 0x00ff00ff) << 8);
4  n = ((n & 0xf0f0f0f0) >>> 4) | ((n & 0x0f0f0f0f) << 4);
5  n = ((n & 0xcccccccc) >>> 2) | ((n & 0x33333333) << 2);
6  n = ((n & 0xaaaaaaaa) >>> 1) | ((n & 0x55555555) << 1);
7  return n >>> 0;
8}

n = 513540756

n

Swap the 16-bit halves.

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