[1 2 3 4 5 6]

train = [1 2 3 4], validation = [5 6] => accuracy = 0.9
train = [1 2 5 6], validation = [3 4] => accuracy = 0.7
train = [3 4 5 6], validation = [1 2] => accuracy = 0.8

data = [1 3 2 4 5 6]

train = [1 3 2 4], validation = [5 6] (the same as before)
train = [1 3 5 6], validation = [2 4] (different)
train = [2 4 5 6], validation = [1 3] (different)