1+ class Trie {
2+ 3+ class TrieNode {
4+ 5+ private TrieNode [] links ;
6+ 7+ private final int R = 26 ;
8+ 9+ private boolean isEnd ;
10+ 11+ public TrieNode () {
12+ links = new TrieNode [R ];
13+ }
14+ 15+ public boolean containsKey (char ch ) {
16+ return links [ch -'a' ] != null ;
17+ }
18+ 19+ public TrieNode get (char ch ) {
20+ return links [ch -'a' ];
21+ }
22+ 23+ public void put (char ch , TrieNode node ) {
24+ links [ch -'a' ] = node ;
25+ }
26+ 27+ public void setEnd () {
28+ isEnd = true ;
29+ }
30+ 31+ public boolean isEnd () {
32+ return isEnd ;
33+ }
34+ }
35+ 36+ private TrieNode root ;
37+ 38+ public Trie () {
39+ root = new TrieNode ();
40+ }
41+ 42+ public void insert (String word ) {
43+ TrieNode node = root ;
44+ for (int i = 0 ; i < word .length (); i ++) {
45+ char currentChar = word .charAt (i );
46+ if (!node .containsKey (currentChar )) {
47+ node .put (currentChar , new TrieNode ());
48+ }
49+ node = node .get (currentChar );
50+ }
51+ node .setEnd ();
52+ }
53+ 54+ private TrieNode searchPrefix (String word ) {
55+ TrieNode node = root ;
56+ for (int i = 0 ; i < word .length (); i ++) {
57+ char curLetter = word .charAt (i );
58+ if (node .containsKey (curLetter )) {
59+ node = node .get (curLetter );
60+ } else {
61+ return null ;
62+ }
63+ }
64+ return node ;
65+ }
66+ 67+ public boolean search (String word ) {
68+ TrieNode node = searchPrefix (word );
69+ return node != null && node .isEnd ();
70+ }
71+ 72+ public boolean startsWith (String prefix ) {
73+ TrieNode node = searchPrefix (prefix );
74+ return node != null ;
75+ }
76+ }
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