Add Design a Trie

Author: marttp

kotlin/Tries/DesignATrie.kt

@@ -0,0 +1,53 @@
+/*
+    Definition of a TrieNode:
+    
+    data class TrieNode(
+        var isWord: Boolean = false,
+        val children: HashMap<Char, TrieNode> = hashMapOf()
+    )
+*/
+class Trie {
+    val root = TrieNode()
+
+    fun insert(word: String) {
+        var node = root
+        for (c in word.toCharArray()) {
+            // For each character in the word, if it's not a child of
+            // the current node, create a new TrieNode for that
+            // character.
+            if (c !in node.children) {
+                node.children[c] = TrieNode()
+            }
+            node = node.children[c]!!
+        }
+        // Mark the last node as the end of a word.
+        node.isWord = true
+    }
+
+    fun search(word: String): Boolean {
+        var node = root
+        for (c in word.toCharArray()) {
+            // For each character in the word, if it's not a child of
+            // the current node, the word doesn't exist in the Trie.
+            if (c !in node.children) {
+                return false
+            }
+            node = node.children[c]!!
+        }
+        // Return whether the current node is marked as the end of the word.
+        return node.isWord
+    }
+
+    fun hasPrefix(prefix: String): Boolean {
+        var node = root
+        for (c in prefix.toCharArray()) {
+            if (c !in node.children) {
+                return false
+            }
+            node = node.children[c]!!
+        }
+        // Once we've traversed the nodes corresponding to each
+        // character in the prefix, return True.
+        return true
+    }
+}

kotlin/Tries/TrieNode.kt

@@ -0,0 +1,4 @@
+data class TrieNode(
+    var isWord: Boolean = false,
+    val children: HashMap<Char, TrieNode> = hashMapOf()
+)