feat: add Trie Data Structure

src/main/java/com/thealgorithms/datastructures/tries/Trie.java

@@ -0,0 +1,83 @@
+package com.thealgorithms.datastructures.tries;
+
+/**
+ * Trie class which holds Strings of characters.
+ *
+ * <a href="https://en.wikipedia.org/wiki/Trie">Wikipedia</a>
+ *
+ * @author <a href="https://github.com/sailok">Sailok Chinta</a>
+ */
+public class Trie {
+    private static final char ROOT_CHAR = '*';
+
+    private final TrieNode root;
+
+    public Trie() {
+        this.root = new TrieNode(ROOT_CHAR);
+    }
+
+    /**
+     * Inserts the word into Trie
+     *
+     * @param word
+     */
+    public void insert(String word) {
+        TrieNode head = root;
+
+        for (int i = 0; i < word.length(); i++) {
+            char c = word.charAt(i);
+
+            if (!head.getChildren().containsKey(c)) {
+                head.getChildren().put(c, new TrieNode(c));
+            }
+
+            head = head.getChildren().get(c);
+        }
+
+        head.setEnd(true);
+    }
+
+    /**
+     * Searches in the Trie if a word exists or not.
+     *
+     * @param word
+     * @return true / false
+     */
+    public boolean search(String word) {
+        TrieNode head = root;
+
+        for (int i = 0; i < word.length(); i++) {
+            char c = word.charAt(i);
+
+            if (!head.getChildren().containsKey(c)) {
+                return false;
+            }
+
+            head = head.getChildren().get(c);
+        }
+
+        return head.isEnd();
+    }
+
+    /**
+     * Searches in the Trie if a prefix exists or not.
+     *
+     * @param prefix
+     * @return true / false
+     */
+    public boolean startsWith(String prefix) {
+        TrieNode head = root;
+
+        for (int i = 0; i < prefix.length(); i++) {
+            char c = prefix.charAt(i);
+
+            if (!head.getChildren().containsKey(c)) {
+                return false;
+            }
+
+            head = head.getChildren().get(c);
+        }
+
+        return true;
+    }
+}

src/main/java/com/thealgorithms/datastructures/tries/TrieNode.java

@@ -0,0 +1,49 @@
+package com.thealgorithms.datastructures.tries;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * TrieNode class which holds the characters and references to its child nodes
+ *
+ * <a href="https://en.wikipedia.org/wiki/Trie">Wikipedia</a>
+ *
+ * @author <a href="https://github.com/sailok">Sailok Chinta</a>
+ */
+public class TrieNode {
+    private Map<Character, TrieNode> children;
+    private char value;
+    private boolean end;
+
+    public TrieNode(char value) {
+        this.value = value;
+        this.children = new HashMap<>();
+        this.end = false;
+    }
+
+    public Map<Character, TrieNode> getChildren() {
+        return children;
+    }
+
+    /*
+    public void setChildren(Map<Character, TrieNode> children) {
+        this.children = children;
+    }
+    */
+
+    public char getValue() {
+        return value;
+    }
+
+    public void setValue(char value) {
+        this.value = value;
+    }
+
+    public boolean isEnd() {
+        return end;
+    }
+
+    public void setEnd(boolean end) {
+        this.end = end;
+    }
+}

src/test/java/com/thealgorithms/datastructures/tries/TrieTest.java

@@ -0,0 +1,36 @@
+package com.thealgorithms.datastructures.tries;
+
+import java.util.List;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class TrieTest {
+    private static final List<String> WORDS = List.of("apple", "app", "rest", "rent", "rental");
+
+    @Test
+    void searchInTrieSuccess() {
+        Trie trie = new Trie();
+
+        for (String word : WORDS) {
+            trie.insert(word);
+        }
+
+        Assertions.assertTrue(trie.search("app"));
+        Assertions.assertTrue(trie.search("apple"));
+        Assertions.assertFalse(trie.search("apply"));
+    }
+
+    @Test
+    void startsWithPrefixInTrieSuccess() {
+        Trie trie = new Trie();
+
+        for (String word : WORDS) {
+            trie.insert(word);
+        }
+
+        Assertions.assertTrue(trie.startsWith("app"));
+        Assertions.assertTrue(trie.startsWith("re"));
+        Assertions.assertTrue(trie.startsWith("rent"));
+        Assertions.assertFalse(trie.startsWith("bike"));
+    }
+}