Why is selection sort faster than bubble sort?

Question

[It is written on Wikipedia](http://en.wikipedia.org/wiki/Selection_sort#Comparison_to_other_sorting_algorithms) that "... selection sort almost always outperforms bubble sort and gnome sort." Can anybody please explain to me why is selection sort considered faster than bubble sort even though both of them have: 1. **Worst case time complexity**: $\\mathcal O(n^2)$ 2. **Number of comparisons**: $\\mathcal O(n^2)$ 3. **Best case time complexity** : * Bubble sort: $\\mathcal O(n)$* Selection sort: $\\mathcal O(n^2)$4. **Average case time complexity** : * Bubble sort: $\\mathcal O(n^2)$* Selection sort: $\\mathcal O(n^2)$

Answer 1

Technically selection sort will always be the same or faster than bubble sort. This is due to the slower nature of bubble sort, bubble sort in some instances will take more iterations to move the same data to a more sorted position, whereas selection sort will always have part of the array sorted instantly.

for example.

selection

6 5 7 3 9

3 5 7 6 9

3 5 7 6 9

3 5 6 7 9

bubble

6 5 7 3 9

5 6 7 3 9

5 6 3 7 9

5 3 6 7 9

3 5 6 7 9

see how long it took to move the 3 to the 0th index in bubble sort?

it is inefficient and lazy compared to selection sort, which is why selection sort finished 1 iteration earlier than bubble in this instance, and could finish at the same time in other cases, however selection sort will NEVER be slower than bubble sort.