Interview cake - Find duplicate (space optimization)

def find_duplicate(array)
    mid = array.size/2
    p array.slice(0, mid)
    p array.slice(mid, array.size)
end


p find_duplicate([1, 2, 5, 7, 2, 46]) #2
p find_duplicate([1, 2, 5, 7, 32, 2, 46]) #2