add trie

README.md

@@ -9,6 +9,7 @@
 * [Hash tables](#htable)
 * [Map](#map)
 * [Linked list](#llist)
+* [Trie](#trie)
 
 ### Stack <a name="stack"></a> 
 ![Stack](pics/stack.jpeg)
@@ -748,4 +749,10 @@
     console.log(util.inspect(myll.head(), {showHidden: false, depth: null})); // Node {element: 'lalala',next: Node {element: 12,next:Node {element: 'lolo',next: Node { element: 34, next: Node { element: 43, next: null } } } } }
     console.log(myll.removeAt(2));      // undefined
     console.log(util.inspect(myll.head(), {showHidden: false, depth: null})); // Node {element: 'lalala',next: Node {element: 12,next: Node { element: 34, next: Node { element: 43, next: null } } } }
-```
+```
+
+
+### Trie <a name="trie"></a> 
+![Trie](pics/trie.png)
+* An use case is to validate if a word in the dictionary
+```javascript

trie.js

@@ -0,0 +1,68 @@
+const Node = function() {
+    this.keys = new Map();
+    this.end = false;
+    this.setEnd = function() { this.end = true };
+    this.isEnd = function() { return this.end };
+}
+
+let Trie = function() {
+    this.root = new Node();
+    this.add = function(input, node = this.root) { // add word to trie
+        if (input.length == 0) {
+            node.setEnd();
+            return;
+        } else if (!node.keys.has(input[0])) {
+            node.keys.set(input[0], new Node());
+            return this.add(input.substr(1), node.keys.get(input[0]));
+        } else {
+            return this.add(input.substr(1), node.keys.get(input[0]));
+        };
+    };
+    this.isWord = function(word) { // check if word is in trie
+        let node = this.root;
+        while (word.length > 1) {
+            if (!node.keys.has(word[0])) {
+                return false;
+            } else {
+                node = node.keys.get(word[0]);
+                word = word.substr(1);
+            };
+        };
+        return (node.keys.has(word) && node.keys.get(word).isEnd()) ? 
+            true : false;
+    };
+
+    this.print = function() {
+        let words = new Array();
+        let search = function(node, string) {
+            if (node.keys.size != 0) {
+                for (let letter of node.keys.keys()) {
+                    search(node.keys.get(letter), string.concat(letter));
+                };
+                if (node.isEnd()) {
+                    words.push(string);
+                };
+            } else {
+                string.length > 0 ? words.push(string) : undefined;
+                return;
+            };
+        };
+        search(this.root, new String());
+        return words.length > 0 ? words : mo;
+    };
+
+};
+
+myTrie = new Trie()
+myTrie.add('ball'); 
+myTrie.add('bat'); 
+myTrie.add('doll'); 
+myTrie.add('dork'); 
+myTrie.add('do'); 
+myTrie.add('dorm')
+myTrie.add('send')
+myTrie.add('sense')
+console.log(myTrie.isWord('doll'));     // true
+console.log(myTrie.isWord('dor'))       // false
+console.log(myTrie.isWord('dorf'))      // false
+console.log(myTrie.print());            // [ 'ball', 'bat', 'doll', 'dork', 'dorm', 'do', 'send', 'sense' ]