If no swapping happens in a pass, it means the list is already:

1. A swap happens only when two neighbours are out of order. 2. A pass with none means no pair was out of order. 3. If there is no swapping in any pass, the list is already sorted. 4. The sorting operation then needs to be stopped. _Source: syllabus Computer Science, Ch 5 'Sorting' and Ch 6 'Searching'_