Answer
The sorted list is $\{1,2,3,4,5,6\}$. Please check the solution to have a look at how the algorithm would work.
Work Step by Step
The key property of the bubble sort is that at the end of iteration $i$, the last $i$ values would be in the correct position. For example, after the first iteration, the greatest value would be at the last location. During each iteration, for some value $m$ and all values of $i$ such that $i < m$, we check $a_i$ and $a_{i+1}$ and interchange if need be.
For this example, the list is $\{6,2,3,1,5,4\}$.
During the first iteration, comparing each pair, we get the following - $\{2,3,1,5,4, \underline{6}\}$. We compare $6$ with each value and it gets to the end of the list.
During the second iteration, comparing each pair, we get the following - $\{2,1,3,4, \underline{5, 6}\}.$ First, $1$ and $3$ get interchanged followed by $4$ and $5$. Notice that even though the last four are in the correct position, we cannot establish this yet after the second iteration. The only thing we know is that $5$ and $6$ are in the valid positions.
During the third iteration, comparing each pair, we get the following - $\{1, 2, 3, \underline {4, 5, 6} \}$. We only make one interchange between $1$ and $2.$
Notice that even though the array is now in the proper order, there are still two more iterations in which nothing changes. Note that exercise $37$ addresses this issue and resolves it.
