Reverse Bits with Group Reversals

Solution: Multiple Group Reversals

abcdefgh -> efghabcd -> ghefcdab -> hgfedcba

Swap first 16 bits with last 16 bits. Then swap first 8 and last 8 within each 16-bit group. Keep going until individual bits swap. This reverses the entire bit sequence.

uint32_t reverseBits(uint32_t n) {
    n = (n<<16) | (n>>16);
    n = ((n & 0xff00ff00) >> 8) | ((n & 0x00ff00ff) << 8);
    n = ((n & 0xf0f0f0f0) >> 4) | ((n & 0x0f0f0f0f) << 4);
    n = ((n & 0xcccccccc) >> 2) | ((n & 0x33333333) << 2);
    n = ((n & 0xaaaaaaaa) >> 1) | ((n & 0x55555555) << 1);
    return n;
}

#bit-manipulation

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