Implement Heap Sort in Erlang

This keynote gives a short intro about how to implement the heap sort algorithm in Erlang.

Topics covered:

1. Represent trees in Erlang
2. The Zipper technique
3. Breadth-first traversal

Transcript

1. Heap Sort in Erlang @daqing 2013-6-22
2. Heap Sort 堆排序 2013-6-22
3. L = [1, 5, 3, 2, 4] 5 1 2 3 4 S = [ , , , , ] 1 2 3 4 2 5 4 3 2 1 4 2013-6-22
4. Algorithm • Build a max-heap from the input list • Put root value into result • Swap root node • loop 2013-6-22
5. Represents a Tree in Erlang 2013-6-22
6. Tree Structure {Value, Left, Right} {Value, {Value, Left, Right}, {Value, Left, Right}} 2013-6-22
7. 5 1 2 3 4 {5, {4, {1, undefined, undefined}, {2, undefined, undefined} }, {3, undefined, undefined} } Max-heap in Erlang 2013-6-22
8. L = [1, 5, 3, 2, 4] 5 1 2 3 4 Build Max-heap 2013-6-22
9. L = [1, 5, 3, 2, 4] Build Max-heap {5, {4, {1, undefined, undefined}, {2, undefined, undefined} }, {3, undefined, undefined} } 2013-6-22
10. Zipper http://ferd.ca/yet-another-article-on-zippers.html 2013-6-22
11. { [ {direction, Value, OtherBranch} | T ], {CurrentVal, CurrentLeft, CurrentRight} } Zipper 2013-6-22
12. Build Max-heap 2013-6-22
13. Swap Root Node 2013-6-22
14. 5 1 2 3 4 1 2 3 4 2 4 3 2 1 Swap Root Node 2013-6-22
15. 5 1 2 3 4 [2, 4, 3, 1] 4 3 2 1 Convert Heap to List 2013-6-22
16. Breadth-first Traversal 2013-6-22
17. 2013-6-22
18. 5 1 2 3 4 [2, 4, 3, 1] 4 3 2 1 Build Max-heap 2013-6-22
19. Algorithm • Build a max-heap from the input list • Put root value into result • Swap root node • loop 2013-6-22
20. 5 1 2 3 4 S = [ , , , , ] 1 2 3 4 2 5 4 3 2 1 4 1 3 2 1 3 2 1 3 1 2 1 2 1 2 1 1 2013-6-22
21. Source Code https://github.com/daqing/algorithms/blob/master/heap_sort/heap_sort.erl 2013-6-22
22. Questions? 2013-6-22
23. Thanks https://github.com/daqing https://github.com/daqing/algorithms @daqing 2013-6-22