[Week5](gmlwls96) Implement Trie prefix Tree

Author: gmlwls96

implement-trie-prefix-tree/gmlwls96.kt

@@ -0,0 +1,43 @@
+class Node() {
+    val map = mutableMapOf<Char, Node?>()
+    var isEnd = false
+}
+
+class Trie() {
+    /** insert, search, startWith 시간 복잡도 : O(n) * */
+    val rootNode = Node()
+    fun insert(word: String) {
+        var currentNode = rootNode
+        word.forEach { char ->
+            if (currentNode.map[char] == null) {
+                currentNode.map[char] = Node()
+            }
+            currentNode = currentNode.map[char]!!
+        }
+        currentNode.isEnd = true
+    }
+
+    fun search(word: String): Boolean {
+        var currentNode = rootNode
+        word.forEach { char ->
+            if (currentNode.map[char] == null) {
+                return false
+            } else {
+                currentNode = currentNode.map[char]!!
+            }
+        }
+        return currentNode.isEnd
+    }
+
+    fun startsWith(prefix: String): Boolean {
+        var currentNode = rootNode
+        prefix.forEach { char ->
+            if (currentNode.map[char] == null) {
+                return false
+            } else {
+                currentNode = currentNode.map[char]!!
+            }
+        }
+        return true
+    }
+}