feat: add Trie class

Author: sailok.chinta

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

@@ -0,0 +1,121 @@
+package com.thealgorithms.tries;
+
+/**
+ * TrieNode class which holds the lowercase letter and references to its child nodes
+ */
+class TrieNode {
+    private static final int CHILDREN_NODE_COUNT = 26;
+    
+    private TrieNode[] children;
+    private char letter;
+    private boolean end;
+
+    public TrieNode(char letter) {
+        this.letter = letter;
+        this.children = new TrieNode[CHILDREN_NODE_COUNT];
+        this.end = false;
+    }
+
+    public TrieNode[] getChildren() {
+        return children;
+    }
+
+    public void setChildren(TrieNode[] children) {
+        this.children = children;
+    }
+
+    public char getLetter() {
+        return letter;
+    }
+
+    public void setLetter(char letter) {
+        this.letter = letter;
+    }
+
+    public boolean isEnd() {
+        return end;
+    }
+
+    public void setEnd(boolean end) {
+        this.end = end;
+    }
+}
+
+/**
+ * Trie class which holds Strings of LowerCase Sensitive characters.
+ */
+public class Trie {
+    private static final char ROOT_CHAR = '*';
+    private static final char BASE_CHAR = 'a';
+
+    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()[c - BASE_CHAR] == null) {
+                head.getChildren()[c - BASE_CHAR] = new TrieNode(c);
+            }
+
+            head = head.getChildren()[c - BASE_CHAR];
+        }
+
+        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()[c - BASE_CHAR] == null) {
+                return false;
+            }
+
+            head = head.getChildren()[c - BASE_CHAR];
+        }
+
+        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()[c - BASE_CHAR] == null) {
+                return false;
+            }
+
+            head = head.getChildren()[c - BASE_CHAR];
+        }
+
+        return true;
+    }
+}