Implementation of trie data structure using java.

data_structures/TrieJava.java

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+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+// A class to store a Trie node
+class Trie
+{
+    // Define the alphabet size (26 characters for `a – z`)
+    private static final int CHAR_SIZE = 26;
+
+    private boolean isLeaf;
+    private List<Trie> children = null;
+
+    // Constructor
+    Trie()
+    {
+        isLeaf = false;
+        children = new ArrayList<>(Collections.nCopies(CHAR_SIZE, null));
+    }
+
+    // Iterative function to insert a string into a Trie
+    public void insert(String key)
+    {
+        System.out.println("Inserting \"" + key + "\"");
+
+        // start from the root node
+        Trie curr = this;
+
+        // do for each character of the key
+        for (char c: key.toCharArray())
+        {
+            // create a new Trie node if the path does not exist
+            if (curr.children.get(c - 'a') == null) {
+                curr.children.set(c - 'a', new Trie());
+            }
+
+            // go to the next node
+            curr = curr.children.get(c - 'a');
+        }
+
+        // mark the current node as a leaf
+        curr.isLeaf = true;
+    }
+
+    // Iterative function to search a key in a Trie. It returns true
+    // if the key is found in the Trie; otherwise, it returns false
+    public boolean search(String key)
+    {
+        System.out.print("Searching \"" + key + "\" : ");
+
+        Trie curr = this;
+
+        // do for each character of the key
+        for (char c: key.toCharArray())
+        {
+            // go to the next node
+            curr = curr.children.get(c - 'a');
+
+            // if the string is invalid (reached end of a path in the Trie)
+            if (curr == null) {
+                return false;
+            }
+        }
+
+        // return true if the current node is a leaf node and the
+        // end of the string is reached
+        return curr.isLeaf;
+    }
+}
+
+class Main
+{
+    public static void main (String[] args)
+    {
+        // construct a new Trie node
+        Trie head = new Trie();
+
+        head.insert("techie");
+        head.insert("techi");
+        head.insert("tech");
+
+        System.out.println(head.search("tech"));            // true
+        System.out.println(head.search("techi"));           // true
+        System.out.println(head.search("techie"));          // true
+        System.out.println(head.search("techiedelight"));   // false
+
+        head.insert("techiedelight");
+
+        System.out.println(head.search("tech"));            // true
+        System.out.println(head.search("techi"));           // true
+        System.out.println(head.search("techie"));          // true
+        System.out.println(head.search("techiedelight"));   // true
+    }
+}