Add trie implementation

Author: sudheerj

src/java1/algorithms/tree/Trie.java

@@ -0,0 +1,63 @@
+package java1.algorithms.tree;
+
+import java.util.HashMap;
+
+class Node {
+    HashMap<Character, Node> children = new HashMap<>();
+    boolean isEnd = false;
+}
+
+public class Trie {
+
+    Node root;
+
+    Trie(){
+        this.root = new Node();
+    }
+
+    //TC: O(n) SC: O(n)
+    public void insert(String word) {
+        Node curr = root;
+        for(char ch: word.toCharArray()) {
+            if(!curr.children.containsKey(ch)) {
+                curr.children.put(ch, new Node());
+            }
+            curr = curr.children.get(ch);
+        }
+        curr.isEnd = true;
+    }
+
+    //TC: O(n) SC: O(1)
+    public boolean search(String word) {
+        Node curr = root;
+        for(char ch: word.toCharArray()) {
+            if(!(curr.children.containsKey(ch))) {
+                return false;
+            }
+            curr = curr.children.get(ch);
+        }
+        return curr.isEnd;
+    }
+
+    //TC: O(n) SC: O(1)
+    public boolean startsWith(String prefix) {
+        Node curr = root;
+        for(char ch: prefix.toCharArray()) {
+            if(!(curr.children.containsKey(ch))) {
+                return false;
+            }
+            curr = curr.children.get(ch);
+        }
+        return true;
+    }
+
+    public static void main(String[] args) {
+        Trie trie = new Trie();
+        trie.insert("apple");
+        System.out.println(trie.search("apple"));
+        System.out.println(trie.search("app"));
+        System.out.println(trie.startsWith("app")); 
+        trie.insert("app");
+        System.out.println(trie.search("app")); 
+    }
+}

src/javascript/algorithms/tree/trie.js

@@ -0,0 +1,56 @@
+class Node {
+    constructor() {
+        this.children = {};
+        this.isEnd = false;
+    }
+}
+
+class Trie {
+    constructor() {
+        this.root = new Node();
+    }
+
+    //TC: O(n) SC: O(n)
+    insert(word) {
+        let curr = this.root;
+        for(let ch of word) {
+            if(!(ch in curr.children)) {
+                curr.children[ch] = new Node();
+            }
+            curr = curr.children[ch];
+        }
+        curr.isEnd = true;
+    }
+
+    //TC: O(n) SC: O(1)
+    search(word) {
+        let curr = this.root;
+        for(let ch of word) {
+            if(!(ch in curr.children)) {
+                return false;
+            }
+            curr = curr.children[ch];
+        }
+        return curr.isEnd;
+    }
+
+    //TC: O(n) SC: O(1)
+    startsWith(prefix) {
+        let curr = this.root;
+        for(let ch of prefix) {
+            if(!(ch in curr.children)) {
+                return false;
+            }
+            curr = curr.children[ch];
+        }
+        return true;
+    }
+}
+
+let trie = new Trie();
+trie.insert("apple");
+console.log(trie.search("apple"));
+console.log(trie.search("app"));
+console.log(trie.startsWith("app")); 
+trie.insert("app");
+console.log(trie.search("app"));