Bubble Sort Algorithm

Activity 10-5 steps through the algorithm for a bubble sort. You may want to gather 4 or 5 items of different sizes and practice sorting them yourself.

Below is the basic algorithm for a bubble sort that sorts in descending order. This description is called pseudo-code because although it is not give in code, it is more code-like than a language spoken by people. You can practically take each sentence and covert it to a programming language and have the algorithm coded.

Figure 10-5: Pseudo Code for the Bubble Sort Algorithm 

Assume the list is not sorted (sorted is set to FALSE)
while(!sorted)
{
   Assume the list is sorted (sorted is set to TRUE)
   Set i to loop through list from first to last - 1
   {
      if list[i] and list[i + 1] are not in the right order
      {
         switch them (called a swap)
         set sorted to FALSE
      }
   }
}
Notice that although the psuedo code does not contain Java-specific syntax, it is somewhat clear to you how to write the code. We will not show the code because it is one of your Programming Assignments at the end of this module.

Let's go through the algorithm for a bubble sort.

Activity 10-6: Bubble Sort Algorithm (Descending)

    One difference between a bubble sort and a selection sort is that a bubble sort switches elements as it goes through the array. Once it completely goes through the array without switching any elements, the array is sorted.

     

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The next activity goes through the bubble sort algorithm, but sorts in ascending order rather than descending order.

Activity 10-6: Bubble Sort Algorithm (Ascending)


















Practice this and the selection sort until you can sort objects using with Then practice the sorts by drawing an array of numbers and sorting that rather than sorting physical objects.

One way to remember the difference between the two sorts is that a bubble sort switches elements as it goes through the list, but a selection sort only swaps once each time through the list.