Added The Trie Data Structure

src/main/java/com/github/pedrovgs/trie/Trie.java

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+package com.github.pedrovgs.trie;
+
+import java.util.HashMap;
+import java.util.Map;
+/**
+ * In computer science, a trie, also called digital tree, radix tree or prefix tree
+ * is a kind of search tree—an ordered tree data structure used to store a dynamic
+ * set or associative array where the keys are usually strings. Unlike
+ * a binary search tree, no node in the tree stores the key associated
+ * with that node; instead, its position in the tree defines the key with which it is associated.
+ * All the descendants of a node have a common prefix of the string associated with that node,
+ * and the root is associated with the empty string. Keys tend to be associated with leaves, though
+ * some inner nodes may correspond to keys of interest.
+**/
+/**
+ * @author Kashish Soni.
+ */
+
+public class Trie {
+    public boolean isEndOfWord;         // used to checkif a string ends here
+    public Map<Character, Trie> m;
+
+    public Trie() {
+        m = new HashMap<Character, Trie>();     // Hashmap used to link char values to Trie Nodes
+    }
+
+    public Trie trieCreateNode() {
+        Trie t = new Trie();
+        t.isEndOfWord = false; // End of Word false by default
+        return t;
+    }
+
+    public void insertIntoTrie(Trie root, String s) { // Function to insert a String into the Trie
+        for (int i = 0; i < s.length(); i++) {
+            if (!root.m.containsKey(s.charAt(i))) { // Checks if The Trie already contains that character or not
+                root.m.put(s.charAt(i), new Trie()); // if not then create a new node for that character
+            }
+            root = root.m.get(s.charAt(i)); // root iterates through the trie
+        }
+        root.isEndOfWord = true; // denotes end of a string/pattern
+    }
+
+    public boolean searchInTrie(Trie root, String s) {
+        for (int i = 0; i < s.length(); i++) {
+            if (!(root.m.containsKey(s.charAt(i)))) { // if a node does not exist in the trie
+                return false; // then return not found
+            }
+            root = root.m.get(s.charAt(i));
+        }
+        if (root.isEndOfWord) {    // The pattern may exist partially in // <- |
+            return true;           // another pattern but this does not  // <- | Can be removed to
+        }                          // mean that the search is complete as// <- | implement pattern in pattern search
+        return false;              // word endings may not match         // <- | change to  return true;
+    }
+
+}

src/test/java/com/github/pedrovgs/trie/TrieTest.java

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+package com.github.pedrovgs.trie;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * @author Kashish Soni.
+ */
+
+public class TrieTest {
+    @Before
+    public void setUp() {
+        new TrieTest();
+    }
+    @Test public void shouldReturnTrueIfStringIsFound() {
+        ArrayList<String> s = new ArrayList<String>();
+        s.add("Kashish");
+        s.add("Pedro");
+        s.add("Lorem");
+        s.add("ipsum");
+        s.add("dolor");
+        s.add("sit");
+        s.add("amet");
+        Trie root = new Trie();
+        for (int i = 0; i < s.size(); i++) {
+            root.insertIntoTrie(root, s.get(i));
+        }
+        assertTrue(root.searchInTrie(root, "Kashish"));
+    }
+    @Test public void shouldReturnTrueIfStringIsFound1() {
+        String s = "Kashish Kashisk Lorem ipsum dolor dolo sit si amrt amet";
+        String[] arr = s.split(" ");
+        Trie root = new Trie();
+        for (int i = 0; i < arr.length; i++) {
+            root.insertIntoTrie(root, arr[i]);
+        }
+       // System.out.println("Code checking");
+        assertTrue(root.searchInTrie(root, "Kashish"));
+        assertTrue(root.searchInTrie(root, "Kashisk"));
+        assertFalse(root.searchInTrie(root, "Kashis"));
+        assertTrue(root.searchInTrie(root, "dolo"));
+    }
+}