Add solution #208

Author: JoshCrozier

README.md

@@ -187,6 +187,7 @@
 205|[Isomorphic Strings](./0205-isomorphic-strings.js)|Easy|
 206|[Reverse Linked List](./0206-reverse-linked-list.js)|Easy|
 207|[Course Schedule](./0207-course-schedule.js)|Medium|
+208|[Implement Trie (Prefix Tree)](./0208-implement-trie-prefix-tree.js)|Medium|
 209|[Minimum Size Subarray Sum](./0209-minimum-size-subarray-sum.js)|Medium|
 211|[Design Add and Search Words Data Structure](./0211-design-add-and-search-words-data-structure.js)|Medium|
 213|[House Robber II](./0213-house-robber-ii.js)|Medium|

solutions/0208-implement-trie-prefix-tree.js

@@ -0,0 +1,68 @@
+/**
+ * 208. Implement Trie (Prefix Tree)
+ * https://leetcode.com/problems/implement-trie-prefix-tree/
+ * Difficulty: Medium
+ *
+ * A trie (pronounced as "try") or prefix tree is a tree data structure used to efficiently store
+ * and retrieve keys in a dataset of strings. There are various applications of this data structure,
+ * such as autocomplete and spellchecker.
+ *
+ * Implement the Trie class:
+ * - Trie() Initializes the trie object.
+ * - void insert(String word) Inserts the string word into the trie.
+ * - boolean search(String word) Returns true if the string word is in the trie (i.e., was inserted
+ *   before), and false otherwise.
+ * - boolean startsWith(String prefix) Returns true if there is a previously inserted string word
+ *   that has the prefix prefix, and false otherwise.
+ */
+
+var Trie = function() {
+  this.root = {};
+};
+
+/**
+ * @param {string} word
+ * @return {void}
+ */
+Trie.prototype.insert = function(word) {
+  let node = this.root;
+  for (const char of word) {
+    if (!node[char]) {
+      node[char] = {};
+    }
+    node = node[char];
+  }
+  node.isWord = true;
+};
+
+/**
+ * @param {string} word
+ * @return {boolean}
+ */
+Trie.prototype.search = function(word) {
+  const node = this.find(word);
+  return node != null && node.isWord === true;
+};
+
+/**
+ * @param {string} prefix
+ * @return {boolean}
+ */
+Trie.prototype.startsWith = function(prefix) {
+  return this.find(prefix) !== null;
+};
+
+/**
+ * @param {string} word
+ * @return {boolean}
+ */
+Trie.prototype.find = function(word) {
+  let node = this.root;
+  for (const char of word) {
+    node = node[char];
+    if (!node) {
+      return null;
+    }
+  }
+  return node;
+};