A power of two has exactly one set bit. Using Brian Kernighan's trick: if n & (n - 1) == 0, then has at most one set bit.
But we also need (since has no set bits but isn't a power of two).
The check is: n > 0 && (n & (n - 1)) == 0.
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$ curl repovive.com/roadmaps/fundamental-algorithms/bit-manipulation/power-of-two-bit-trick
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