Checking in Trie implementation

Author: deepak-malik

README.md

@@ -99,7 +99,8 @@ Below topics/problems are covered as of now.
 - [X] [Dequeue](../master/src/com/deepak/data/structures/Queue/Dequeue.java)
 
 **11. Trie**
-- [ ] Introduction
+- [X] [Introduction](../master/src/com/deepak/data/structures/Trie/TrieIntroduction.md)
+- [X] [Implement Trie](../master/src/com/deepak/data/structures/Trie/TrieImplementation.java)
 
 **12. Treap**
 - [ ] Introduction

src/com/deepak/data/structures/Stack/ArrayBasedStack.java

@@ -1,5 +1,5 @@
 /**
- * Data-Structures-And-Algorithms-in-Java
+ * Data-Structures-in-Java
  * ArrayBasedStack.java
  */
 package com.deepak.data.structures.Stack;

src/com/deepak/data/structures/Trie/TrieImplementation.java

@@ -0,0 +1,123 @@
+/**
+ * Data-Structures-In-Java
+ * TrieImplementation.java
+ */
+package com.deepak.data.structures.Trie;
+
+import java.util.HashMap;
+
+/**
+ * Class to hold Trie implementation
+ * Not making it generic since keys are usually strings
+ *
+ * @author Deepak
+ */
+public class TrieImplementation {
+
+	/**
+	 * Root Node
+	 */
+	private TrieNode root;
+
+	/**
+	 * Default Constructor
+	 */
+	public TrieImplementation() {
+		root = new TrieNode();
+	}
+
+	/**
+	 * Method to insert a word in Trie
+	 * @param word
+	 */
+	public void insert(String word) {
+		HashMap<Character, TrieNode> children = root.children;
+		for (int i = 0; i < word.length(); i++) {
+			char character = word.charAt(i);
+			TrieNode node = null;
+			if (children.containsKey(character)) {
+				node = children.get(character);
+			} else {
+				node = new TrieNode(character);
+				children.put(character, node);
+			}
+			children = node.children;
+			if (i == word.length() - 1) {
+				node.isLeaf = true;
+			}
+		}
+	}
+
+	/**
+	 * Method to check if a word in Trie starts with the given prefix
+	 * @param prefix
+	 * @return {@link boolean}
+	 */
+	public boolean startsWith(String prefix) {
+		if (searchNode(prefix) != null) {
+			return true;
+		}
+		return false;
+	}
+
+	/**
+	 * Method to search TrieNode based on the word
+	 * @param word
+	 * @return {@link TrieNode}
+	 */
+	public TrieNode searchNode(String word) {
+		HashMap<Character, TrieNode> children = root.children;
+		TrieNode node = null;
+		for (int i = 0; i < word.length(); i++) {
+			char character = word.charAt(i);
+			if (children.containsKey(character)) {
+				node = children.get(character);
+				children = node.children;
+			} else {
+				return null;
+			}
+		}
+		return node;
+	}
+
+	/**
+	 * Method to search the given word in the Trie
+	 * @param word
+	 * @return {@link boolean}
+	 */
+	public boolean searchWord(String word) {
+		TrieNode node = searchNode(word);
+		if (null != node && node.isLeaf) {
+			return true;
+		}
+		return false;
+	}
+
+	/**
+	 * Static class TrieNode
+	 * 
+	 * @author Deepak
+	 */
+	public static class TrieNode {
+
+		/* Attributes of TrieNode*/
+		char c;
+		HashMap<Character, TrieNode> children = new HashMap<>();
+		boolean isLeaf;
+
+		/**
+		 * Default Constructor
+		 */
+		public TrieNode() {}
+
+		/**
+		 * Parameterized Constructor
+		 * @param c
+		 */
+		public TrieNode(char c) {
+			this.c = c;
+		}
+
+	}
+
+}

src/com/deepak/data/structures/Trie/TrieIntroduction.md

@@ -0,0 +1,33 @@
+/**
+ * Data-Structures-in-Java
+ * TrieTest.java
+ */
+package com.deepak.data.structures.Trie;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Test cases to test Trie Data Structure
+ * 
+ * @author Deepak
+ */
+public class TrieTest {
+
+	/**
+	 * Test case to test all the Trie functionalities
+	 */
+	@Test
+	public void testTrieFunctionality() {
+		TrieImplementation trie = new TrieImplementation();
+		trie.insert("Zebra");
+		trie.insert("Cat");
+		trie.insert("Dog");
+		Assert.assertTrue(trie.startsWith("D"));
+		Assert.assertNotNull(trie.searchNode("Cat"));
+		Assert.assertNotNull(trie.searchNode("Dog"));
+		Assert.assertTrue(trie.startsWith("Zebra"));
+		Assert.assertFalse(trie.startsWith("M"));
+	}
+
+}