Fast midpoint between two integers without overflow

Re:Fast midpoint between two integers without overflow by mojuba on Wednesday December 07, 2022 @08:20PM (#33902858)

One of the solutions I came up with back in the day, without googling was this:

    int avg(int a, int b) {
        if ((a < 0) != (b < 0)) // not the same sign?
            return (a + b) / 2;
        else
            return a + (b - a) / 2;
    }

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Re:Fast midpoint between two integers without overflow by DenisM on Thursday December 08, 2022 @02:09AM (#33905108)

It’s tricky.

This will round (-2,-1) to -2, i.e. away from zero. For comparison, if we perform the canonical (a+b)/2 instead it will round to -1, i.e. towards zero.

Now, the problem statement does not tell us how to round, so you’re technically correct, but the inconsistency bothers me.

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