before sorting : 9 -> 8 -> 7 -> 6 -> 5 -> 4 -> NULL
after sorting  : 4 -> 5 -> 6 -> 7 -> 8 -> 9 -> NULL
after insert   : 4 -> 5 -> 6 -> 7 -> 8 -> 9 -> 0 -> NULL
passes: 6, swaps: 15
