Implement Trie

Author: Romanow

README.md

@@ -46,10 +46,9 @@
 15. [Game of Life](https://leetcode.com/problems/game-of-life/) – [solution](src/main/kotlin/ru/romanow/medium/GameOfLife.kt), [test](src/test/kotlin/ru/romanow/medium/GameOfLifeTest.kt)
 16. [Delete Node in a Linked List](https://leetcode.com/problems/delete-node-in-a-linked-list/) – [solution](src/main/kotlin/ru/romanow/medium/DeleteNodeInALinkedList.kt), [test](src/test/kotlin/ru/romanow/medium/DeleteNodeInALinkedListTest.kt)
 17. [Longest Common Subsequence](https://leetcode.com/problems/longest-common-subsequence/) – [solution](src/main/kotlin/ru/romanow/medium/LongestCommonSubsequence.kt), [test](src/test/kotlin/ru/romanow/medium/LongestCommonSubsequenceTest.kt)
-18. [Delete Node in a Binary Search Tree](https://leetcode.com/problems/delete-node-in-a-bst/) – [solution](src/main/kotlin/ru/romanow/medium/DeleteNodeInABalancedSearchTree.kt), [test](src/test/kotlin/ru/romanow/medium/DeleteNodeInABalancedSearchTreeTest.kt)
-19. [Decode String](https://leetcode.com/problems/decode-string/) – [solution](src/main/kotlin/ru/romanow/medium/DecodeString.kt), [test](src/test/kotlin/ru/romanow/medium/DecodeStringTest.kt)
-20. [Determine if Two Strings Are Close](https://leetcode.com/problems/determine-if-two-strings-are-close/) – [solution](src/main/kotlin/ru/romanow/medium/DetermineIfTwoStringsAreClose.kt), [test](src/test/kotlin/ru/romanow/medium/DetermineIfTwoStringsAreCloseTest.kt)
-21. [Removing Stars From a String](https://leetcode.com/problems/removing-stars-from-a-string/) – [solution](src/main/kotlin/ru/romanow/medium/RemovingStarsFromAString.kt), [test](src/test/kotlin/ru/romanow/medium/RemovingStarsFromAStringTest.kt)
+18. [Decode String](https://leetcode.com/problems/decode-string/) – [solution](src/main/kotlin/ru/romanow/medium/DecodeString.kt), [test](src/test/kotlin/ru/romanow/medium/DecodeStringTest.kt)
+19. [Determine if Two Strings Are Close](https://leetcode.com/problems/determine-if-two-strings-are-close/) – [solution](src/main/kotlin/ru/romanow/medium/DetermineIfTwoStringsAreClose.kt), [test](src/test/kotlin/ru/romanow/medium/DetermineIfTwoStringsAreCloseTest.kt)
+20. [Removing Stars From a String](https://leetcode.com/problems/removing-stars-from-a-string/) – [solution](src/main/kotlin/ru/romanow/medium/RemovingStarsFromAString.kt), [test](src/test/kotlin/ru/romanow/medium/RemovingStarsFromAStringTest.kt)
 
 ## Hard level
 

src/main/kotlin/ru/romanow/algorithms/BinarySearchTree.kt

@@ -8,11 +8,12 @@ class BinarySearchTree {
     fun get(key: Int): Int? {
         var current = root
         while (current != null) {
-            current = when {
-                key < current.key -> current.left
-                key > current.key -> current.right
-                else -> return current.value
-            }
+            current =
+                when {
+                    key < current.key -> current.left
+                    key > current.key -> current.right
+                    else -> return current.value
+                }
         }
         return null
     }

src/main/kotlin/ru/romanow/algorithms/RedBlackTree.kt

@@ -8,11 +8,12 @@ class RedBlackTree {
     fun get(key: Int): Int? {
         var current = root
         while (current != null) {
-            current = when {
-                key < current.key -> current.left
-                key > current.key -> current.right
-                else -> return current.value
-            }
+            current =
+                when {
+                    key < current.key -> current.left
+                    key > current.key -> current.right
+                    else -> return current.value
+                }
         }
         return null
     }
@@ -24,5 +25,4 @@ class RedBlackTree {
         override var left: TreeNode?,
         override var right: TreeNode?
     ) : TNode<TreeNode>
-
 }

src/main/kotlin/ru/romanow/medium/DeleteNodeInABalancedSearchTree.kt

@@ -14,14 +14,34 @@ package ru.romanow.medium
  * [https://leetcode.com/problems/implement-trie-prefix-tree/](https://leetcode.com/problems/implement-trie-prefix-tree/)
  */
 class PrefixTree {
+    private val root = TrieNode()
+
     fun insert(word: String) {
+        var node = root
+        for (chr in word) {
+            node = node.children.getOrPut(chr) { TrieNode() }
+        }
+        node.isEndOfWord = true
     }
 
     fun search(word: String): Boolean {
-        return false
+        return find(word)?.isEndOfWord == true
     }
 
     fun startsWith(prefix: String): Boolean {
-        return false
+        return find(prefix) != null
+    }
+
+    private fun find(word: String): TrieNode? {
+        var node = root
+        for (chr in word) {
+            node = node.children[chr] ?: return null
+        }
+        return node
     }
+
+    private data class TrieNode(
+        val children: MutableMap<Char, TrieNode> = mutableMapOf(),
+        var isEndOfWord: Boolean = false,
+    )
 }

src/main/kotlin/ru/romanow/medium/PrefixTree.kt

@@ -1,6 +1,7 @@
 package ru.romanow.models
 
-import java.util.*
+import java.util.LinkedList
+import kotlin.collections.ArrayList
 
 interface TNode<T : TNode<T>> {
     var key: Int