[0, 1, 0, 0, 0]
[0, 1, 2, 0, 0]
[0, 1, 2, 3, 0]
[4, 1, 2, 3, 0]
[4, 5, 2, 3, 1]
[4, 5, 2, 3, 1]
4 5 2 3 1