Cleanup.

README.md

@@ -9,6 +9,7 @@
 3. [Stack](https://github.com/trekhleb/javascript-algorithms/tree/master/src/data-structures/stack)
 4. [Hash Table](https://github.com/trekhleb/javascript-algorithms/tree/master/src/data-structures/hash-table)
 5. [Heap](https://github.com/trekhleb/javascript-algorithms/tree/master/src/data-structures/heap)
+5. [Trie](https://github.com/trekhleb/javascript-algorithms/tree/master/src/data-structures/trie)
 
 ## [Algorithms](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms)
 

src/data-structures/trie/Trie.js

@@ -0,0 +1,45 @@
+import TrieNode from './TrieNode';
+
+const HEAD_CHARACTER = '*';
+
+export default class Trie {
+  constructor() {
+    this.head = new TrieNode(HEAD_CHARACTER);
+  }
+
+  addWord(word) {
+    const characters = Array.from(word);
+    let currentNode = this.head;
+    for (let charIndex = 0; charIndex < characters.length; charIndex += 1) {
+      const isComplete = charIndex === characters.length - 1;
+      currentNode = currentNode.addChild(characters[charIndex], isComplete);
+    }
+  }
+
+  suggestNextCharacters(word) {
+    const lastCharacter = this.getLastCharacterNode(word);
+
+    if (!lastCharacter) {
+      return null;
+    }
+
+    return lastCharacter.suggestChildren();
+  }
+
+  doesWordExists(word) {
+    return !!this.getLastCharacterNode(word);
+  }
+
+  getLastCharacterNode(word) {
+    const characters = Array.from(word);
+    let currentNode = this.head;
+    for (let charIndex = 0; charIndex < characters.length; charIndex += 1) {
+      if (!currentNode.hasChild(characters[charIndex])) {
+        return null;
+      }
+      currentNode = currentNode.getChild(characters[charIndex]);
+    }
+
+    return currentNode;
+  }
+}

src/data-structures/trie/TrieNode.js

@@ -0,0 +1,39 @@
+export default class TrieNode {
+  constructor(character, isCompleteWord = false) {
+    this.character = character;
+    this.isCompleteWord = isCompleteWord;
+    this.children = {};
+  }
+
+  getChild(character) {
+    if (!Object.prototype.hasOwnProperty.call(this.children, character)) {
+      return null;
+    }
+
+    return this.children[character];
+  }
+
+  addChild(character, isCompleteWord = false) {
+    if (!this.children[character]) {
+      this.children[character] = new TrieNode(character, isCompleteWord);
+    }
+
+    return this.children[character];
+  }
+
+  hasChild(character) {
+    return !!this.children[character];
+  }
+
+  suggestChildren() {
+    return Object.keys(this.children);
+  }
+
+  toString() {
+    let childrenAsString = Object.keys(this.children).toString();
+    childrenAsString = childrenAsString ? `:${childrenAsString}` : '';
+    const isCompleteString = this.isCompleteWord ? '*' : '';
+
+    return `${this.character}${isCompleteString}${childrenAsString}`;
+  }
+}

src/data-structures/trie/__test__/Trie.test.js

@@ -0,0 +1,51 @@
+import Trie from '../Trie';
+
+describe('Trie', () => {
+  it('should create trie', () => {
+    const trie = new Trie();
+
+    expect(trie).toBeDefined();
+    expect(trie.head.toString()).toBe('*');
+  });
+
+  it('should add words to trie', () => {
+    const trie = new Trie();
+
+    trie.addWord('cat');
+
+    expect(trie.head.toString()).toBe('*:c');
+    expect(trie.head.getChild('c').toString()).toBe('c:a');
+
+    trie.addWord('car');
+    expect(trie.head.toString()).toBe('*:c');
+    expect(trie.head.getChild('c').toString()).toBe('c:a');
+    expect(trie.head.getChild('c').getChild('a').toString()).toBe('a:t,r');
+    expect(trie.head.getChild('c').getChild('a').getChild('t').toString()).toBe('t*');
+  });
+
+  it('should suggests next characters', () => {
+    const trie = new Trie();
+
+    trie.addWord('cat');
+    trie.addWord('cats');
+    trie.addWord('car');
+    trie.addWord('caption');
+
+    expect(trie.suggestNextCharacters('ca')).toEqual(['t', 'r', 'p']);
+    expect(trie.suggestNextCharacters('cat')).toEqual(['s']);
+    expect(trie.suggestNextCharacters('cab')).toBeNull();
+  });
+
+  it('should check if word exists', () => {
+    const trie = new Trie();
+
+    trie.addWord('cat');
+    trie.addWord('cats');
+    trie.addWord('car');
+    trie.addWord('caption');
+
+    expect(trie.doesWordExists('cat')).toBeTruthy();
+    expect(trie.doesWordExists('cap')).toBeTruthy();
+    expect(trie.doesWordExists('call')).toBeFalsy();
+  });
+});

src/data-structures/trie/__test__/TrieNode.test.js

@@ -0,0 +1,51 @@
+import TrieNode from '../TrieNode';
+
+describe('TrieNode', () => {
+  it('should create trie node', () => {
+    const trieNode = new TrieNode('c', true);
+
+    expect(trieNode.character).toBe('c');
+    expect(trieNode.isCompleteWord).toBeTruthy();
+    expect(trieNode.toString()).toBe('c*');
+  });
+
+  it('should add child nodes', () => {
+    const trieNode = new TrieNode('c');
+
+    trieNode.addChild('a', true);
+    trieNode.addChild('o');
+
+    expect(trieNode.toString()).toBe('c:a,o');
+  });
+
+  it('should get child nodes', () => {
+    const trieNode = new TrieNode('c');
+
+    trieNode.addChild('a');
+    trieNode.addChild('o');
+
+    expect(trieNode.getChild('a').toString()).toBe('a');
+    expect(trieNode.getChild('o').toString()).toBe('o');
+    expect(trieNode.getChild('b')).toBeNull();
+  });
+
+  it('should check if node has specific child', () => {
+    const trieNode = new TrieNode('c');
+
+    trieNode.addChild('a');
+    trieNode.addChild('o');
+
+    expect(trieNode.hasChild('a')).toBeTruthy();
+    expect(trieNode.hasChild('o')).toBeTruthy();
+    expect(trieNode.hasChild('b')).toBeFalsy();
+  });
+
+  it('should suggest next children', () => {
+    const trieNode = new TrieNode('c');
+
+    trieNode.addChild('a');
+    trieNode.addChild('o');
+
+    expect(trieNode.suggestChildren()).toEqual(['a', 'o']);
+  });
+});