Branchless code that maps zero, negative, and positive to 0, 1, 2

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Branchless (at the language level) code that maps negative to -1, zero to 0 and positive to +1 looks as follows

int c = (n > 0) - (n < 0);

if you need a different mapping you can simply use an explicit map to remap it

const int MAP[] = { 1, 0, 2 };
int c = MAP[(n > 0) - (n < 0) + 1];

or, for the requested mapping, use some numerical trick like

int c = 2 * (n > 0) + (n < 0);

(It is obviously very easy to generate any mapping from this as long as 0 is mapped to 0. And the code is quite readable. If 0 is mapped to something else, it becomes more tricky and less readable.)

As an additinal note: comparing two integers by subtracting one from another at C language level is a flawed technique, since it is generally prone to overflow. The beauty of the above methods is that they can immedately be used for “subtractionless” comparisons, like 

int c = 2 * (x > y) + (x < y);

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