Fastest way of finding the middle value of a triple?

Question

Given is an array of three numeric values and I'd like to know the middle value of the three.

The question is, what is the fastest way of finding the middle of the three?

My approach is this kind of pattern - as there are three numbers there are six permutations:

if (array[randomIndexA] >= array[randomIndexB] &&
    array[randomIndexB] >= array[randomIndexC])

It would be really nice, if someone could help me out finding a more elegant and faster way of doing this.

Answer 1

There's an answer here using min/max and no branches (https://stackoverflow.com/a/14676309/2233603). Actually 4 min/max operations are enough to find the median, there's no need for xor's:

median = max(min(a,b), min(max(a,b),c));

Though, it won't give you the median value's index...

Breakdown of all cases:

a b c
1 2 3   max(min(1,2), min(max(1,2),3)) = max(1, min(2,3)) = max(1, 2) = 2
1 3 2   max(min(1,3), min(max(1,3),2)) = max(1, min(3,2)) = max(1, 2) = 2
2 1 3   max(min(2,1), min(max(2,1),3)) = max(1, min(2,3)) = max(1, 2) = 2
2 3 1   max(min(2,3), min(max(2,3),1)) = max(2, min(3,1)) = max(2, 1) = 2
3 1 2   max(min(3,1), min(max(3,1),2)) = max(1, min(3,2)) = max(1, 2) = 2
3 2 1   max(min(3,2), min(max(3,2),1)) = max(2, min(3,1)) = max(2, 1) = 2