CS253: Tries (2019)

https://github.com/emory-courses/cs253

Transcript

1. Tries Data Structures and Algorithms Emory University Jinho D. Choi https://github.com/emory-courses/cs253
3. {"she", "shell", "see", "shore", "selling", "sell"}
5. public class TrieNode<T> { private Map<Character, TrieNode<T>> children; private TrieNode<T> parent; private boolean end_state; private char key; private T value; public TrieNode(TrieNode<T> parent, char key) { children = new HashMap<Character, TrieNode<T>>(); setEndState(false); setParent(parent); setKey(key); setValue(null); } <T> value end_state
6. TrieNode.java public TrieNode<T> getChild(char key) { return children.get(key); } public TrieNode<T> addChild(char key) { TrieNode<T> child = getChild(key); if (child == null) { child = new TrieNode<T>(this, key); children.put(key, child); } return child; } public TrieNode<T> removeChild(char key) { return children.remove(key); } get() add() remove()
7. Trie.java public class Trie<T> { private TrieNode<T> root; public Trie() { root = new TrieNode<>(null, (char) 0); } public T get(String key) { TrieNode<T> node = find(key); return (node != null && node.isEndState()) ? node.getValue() : null; } public TrieNode<T> find(String key) { char[] array = key.toCharArray(); TrieNode<T> node = root; for (int i = 0; i < key.length(); i++) { node = node.getChild(array[i]); if (node == null) return null; } return node; } (char)0 find()
8. Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"}
9. Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅
10. Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅
11. Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅
12. Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅
13. Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ h ∅
14. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ h ∅
15. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅
16. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅
17. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅
18. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅
19. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅
20. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1
21. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1
22. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1
23. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1 e ∅
24. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1 e ∅ e ∅
25. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1 e ∅ e ∅ 2
26. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1 e ∅ e ∅ 2
27. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1 e ∅ e ∅ 2
28. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1 e ∅ e ∅ 2 o ∅
29. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1 e ∅ e ∅ 2 o ∅ r ∅
30. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1 e ∅ e ∅ 2 o ∅ r ∅ e ∅
31. e ∅ Trie - Put 2 {“she”,”shell”,"see","shore","selling","sell"} ∅ ∅ s ∅ 0 h ∅ l ∅ l ∅ 1 e ∅ e ∅ 2 o ∅ r ∅ e ∅ 3
32. public T put(String key, T value) { char[] array = key.toCharArray(); TrieNode<T> node = root; for (int i = 0; i < key.length(); i++) node = node.addChild(array[i]); node.setEndState(true); return node.setValue(value); }
33. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ l 1 e ∅ e 2 o ∅ r ∅ e ∅ 3
34. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ l 1 e ∅ e 2 o ∅ r ∅ e ∅ 3 “see”
35. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ l 1 e ∅ e 2 o ∅ r ∅ e ∅ 3 “see”
36. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ l 1 e ∅ o ∅ r ∅ e ∅ 3 “see”
37. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ l 1 o ∅ r ∅ e ∅ 3 “see”
38. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ l 1 o ∅ r ∅ e ∅ 3 “see” ”she”
39. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ l 1 o ∅ r ∅ e ∅ 3 “see” ”she”
40. Trie - Remove 3 e 0 ∅ ∅ s ∅ ∅ h ∅ l ∅ l 1 o ∅ r ∅ e ∅ 3 “see” ”she”
41. Trie - Remove 3 e 0 ∅ ∅ s ∅ ∅ h ∅ l ∅ l 1 o ∅ r ∅ e ∅ 3 “see” ”she” ”shell”
42. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ l 1 o ∅ r ∅ e ∅ 3 “see” ”she” ”shell”
43. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ l 1 o ∅ r ∅ e ∅ 3 “see” ”she” ”shell”
44. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ l ∅ o ∅ r ∅ e ∅ 3 “see” ”she” ”shell”
45. Trie - Remove 3 e 0 ∅ ∅ s ∅ h ∅ o ∅ r ∅ e ∅ 3 “see” ”she” ”shell”
46. public boolean remove(String key) { TrieNode<T> node = find(key); if (node == null || !node.isEndState()) // node doesn't exist return false; if (node.hasChildren()) { // node to be removed as children node.setEndState(false); return true; } TrieNode<T> parent = node.getParent(); while (parent != null) { // remove iteratively parent.removeChild(node.getKey()); if (parent.hasChildren() || parent.isEndState()) // another word break; else { node = parent; parent = parent.getParent(); } } return true; }