Computer Programming Concepts and Visual Basic David I. Schneider

■ BUBBLE SORT
The bubble sort is an algorithm that compares adjacent items and swaps those that are out of
order. If this process is repeated enough times, the list will be ordered. Let’s carry out this
process on the list Pebbles, Barney, Wilma, Fred, Dino. The steps for each pass through the list
are as follows:
1. Compare the first and second items. If they are out of order, swap them.
2. Compare the second and third items. If they are out of order, swap them.
3. Repeat this pattern for all remaining pairs. The final comparison and possible
swap are between the second-to-last and last elements.
The first time through the list, this process is repeated to the end of the list. This is called
the first pass. After the first pass, the last item (Wilma) will be in its proper position. Therefore,
the second pass does not have to consider it and so requires one less comparison. At the
end of the second pass, the last two items will be in their proper position. (The items that
must have reached their proper position have been underlined.) Each successive pass requires
one less comparison. After four passes, the last four items will be in their proper positions,
and hence, the first will be also.
Sorting and Searching 185