C one line bit manipulation solution with explanation

  • 3
    bool isPowerOfFour(int num) {
        return (!(num & (-num) ^ num)) && (num & 0x55555555);
    • num & (-num) will get the last non-zero bit;
    • ^ num will flip num with that bit, if num is power of 2, (num) & (-num) ^ num should be 0;
    • num & 0x55555555 will further make sure that num is power of 4, because 0x55555555 is 0b01010101010101010101010101010101 in binary.

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