Trie Examples (#3466)

* Implement Trie * Implement TrieTest * Delete testDelete method * Refactorings * Refactor Trie * Refactor TrieNode * Refactor Trie
2018-01-20 11:54:24 +01:00
parent 7e7ccc7eb3
commit 0293c65f77
3 changed files with 175 additions and 0 deletions
--- a/core-java/src/main/java/com/baeldung/trie/Trie.java
+++ b/core-java/src/main/java/com/baeldung/trie/Trie.java
@@ -0,0 +1,76 @@
+package com.baeldung.trie;
+
+public class Trie {
+    private TrieNode root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    public void insert(String word) {
+        TrieNode current = root;
+        for (int i = 0; i < word.length(); i++) {
+            char ch = word.charAt(i);
+            TrieNode node = current.getChildren()
+              .get(ch);
+            if (node == null) {
+                node = new TrieNode();
+                current.getChildren()
+                  .put(ch, node);
+            }
+            current = node;
+        }
+        current.setEndOfWord(true);
+    }
+
+    public boolean find(String word) {
+        TrieNode current = root;
+        for (int i = 0; i < word.length(); i++) {
+            char ch = word.charAt(i);
+            TrieNode node = current.getChildren()
+              .get(ch);
+            if (node == null) {
+                return false;
+            }
+            current = node;
+        }
+        return current.isEndOfWord();
+    }
+
+    public void delete(String word) {
+        delete(root, word, 0);
+    }
+
+    private boolean delete(TrieNode current, String word, int index) {
+        if (index == word.length()) {
+            if (!current.isEndOfWord()) {
+                return false;
+            }
+            current.setEndOfWord(false);
+            return current.getChildren()
+              .size() == 0;
+        }
+        char ch = word.charAt(index);
+        TrieNode node = current.getChildren()
+          .get(ch);
+        if (node == null) {
+            return false;
+        }
+        boolean shouldDeleteCurrentNode = delete(node, word, index + 1);
+
+        if (shouldDeleteCurrentNode) {
+            current.getChildren()
+              .remove(ch);
+            return current.getChildren().isEmpty();
+        }
+        return false;
+    }
+
+    public boolean containsNode(String word) {
+        return find(word);
+    }
+
+    public boolean isEmpty() {
+        return root == null;
+    }
+}
--- a/core-java/src/main/java/com/baeldung/trie/TrieNode.java
+++ b/core-java/src/main/java/com/baeldung/trie/TrieNode.java
@@ -0,0 +1,31 @@
+package com.baeldung.trie;
+
+import java.util.HashMap;
+import java.util.Map;
+
+class TrieNode {
+    private Map<Character, TrieNode> children;
+    private boolean endOfWord;
+
+    public TrieNode() {
+        children = new HashMap<>();
+        endOfWord = false;
+    }
+
+    public Map<Character, TrieNode> getChildren() {
+        return children;
+    }
+
+    public void setChildren(Map<Character, TrieNode> children) {
+        this.children = children;
+    }
+
+    public boolean isEndOfWord() {
+        return endOfWord;
+    }
+
+    public void setEndOfWord(boolean endOfWord) {
+        this.endOfWord = endOfWord;
+    }
+
+}