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| 1 | +package leetcode2018; |
| 2 | + |
| 3 | +import java.util.HashMap; |
| 4 | +import java.util.Map; |
| 5 | + |
| 6 | +public class ImplementPrefixTree { |
| 7 | + private TrieNode root; |
| 8 | + /** Initialize your data structure here. */ |
| 9 | + public ImplementPrefixTree() { |
| 10 | + root = new TrieNode('0'); |
| 11 | + } |
| 12 | + |
| 13 | + /** Inserts a word into the trie. */ |
| 14 | + public void insert(String word) { |
| 15 | + TrieNode currentRoot = root; |
| 16 | + int i = 0; |
| 17 | + for(char c: word.toCharArray()){ |
| 18 | + if(!currentRoot.children.containsKey(c)){ |
| 19 | + TrieNode node = new TrieNode(c); |
| 20 | + currentRoot.children.put(c, node); |
| 21 | + } |
| 22 | + |
| 23 | + currentRoot = currentRoot.children.get(c); |
| 24 | + i++; |
| 25 | + currentRoot.word = word.substring(0,i); |
| 26 | + if(word.length()==i){ |
| 27 | + currentRoot.isComplete = true; |
| 28 | + } |
| 29 | + |
| 30 | + } |
| 31 | + } |
| 32 | + |
| 33 | + /** Returns if the word is in the trie. */ |
| 34 | + public boolean search( String word) { |
| 35 | + TrieNode node = searchHelper(word); |
| 36 | + if(node==null) return false; |
| 37 | + return node.isComplete; |
| 38 | + } |
| 39 | + |
| 40 | + /** Returns if there is any word in the trie that starts with the given prefix. */ |
| 41 | + public boolean startsWith(String prefix) { |
| 42 | + return searchHelper(prefix)!=null; |
| 43 | + } |
| 44 | + |
| 45 | + public TrieNode searchHelper(String word){ |
| 46 | + TrieNode node = root; |
| 47 | + for(char c: word.toCharArray()){ |
| 48 | + if(node.children.containsKey(c)){ |
| 49 | + node = node.children.get(c); |
| 50 | + }else { |
| 51 | + return null; |
| 52 | + } |
| 53 | + } |
| 54 | + return node; |
| 55 | + } |
| 56 | + |
| 57 | + |
| 58 | + class TrieNode{ |
| 59 | + char val; |
| 60 | + Map<Character, TrieNode> children; |
| 61 | + String word; |
| 62 | + boolean isComplete; |
| 63 | + TrieNode(char val){ |
| 64 | + this.val=val; |
| 65 | + this.children = new HashMap<>(); |
| 66 | + this.word= ""; |
| 67 | + this.isComplete = false; |
| 68 | + } |
| 69 | + } |
| 70 | +} |
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