[WEEK6](gmlwls96) Design Add and Search Words Data Structure

Author: gmlwls96

design-add-and-search-words-data-structure/gmlwls96.kt

@@ -0,0 +1,48 @@
+class Node() {
+    val map = mutableMapOf<Char, Node?>()
+    var isEnd = false
+}
+
+class WordDictionary() {
+
+    val rootNode = Node()
+
+    // 시간 : O(n), 공간 : O(n)
+    fun addWord(word: String) {
+        var currentNode = rootNode
+        for (i in word.indices) {
+            val char = word[i]
+            if (currentNode.map[char] == null) {
+                currentNode.map[char] = Node()
+            }
+            currentNode = currentNode.map[char]!!
+        }
+        currentNode.isEnd = true
+    }
+
+    // 시간 : O(26*n), 공간: O(n)
+    fun search(word: String): Boolean {
+        return dfs(
+            pos = 0,
+            word = word,
+            node = rootNode
+        )
+    }
+
+    fun dfs(pos: Int, word: String, node: Node): Boolean {
+        var result = false
+        val char = word[pos]
+        val isLast = word.lastIndex == pos
+        node.map.forEach {
+            if (char == '.' || char == it.key) {
+                if (isLast) {
+                    result = true
+                    return@forEach
+                } else {
+                    result = result or dfs(pos + 1, word, it.value!!)
+                }
+            }
+        }
+        return result
+    }
+}