DFS 사용

Author: YeonguChoe

design-add-and-search-words-data-structure/yeonguchoe.cs

@@ -0,0 +1,67 @@
+public class LetterNode
+{
+    public LetterNode[] Alphabet { get; } = new LetterNode[26]; // Initialize to null
+    public bool IsEnd { get; set; }
+}
+
+public class WordDictionary
+{
+    private LetterNode root;
+
+    public WordDictionary()
+    {
+        root = new LetterNode();
+    }
+
+    public void AddWord(string word)
+    {
+        LetterNode currentNode = root;
+        foreach (char c in word)
+        {
+            int index = c - 'a';
+            if (currentNode.Alphabet[index] == null)
+            {
+                currentNode.Alphabet[index] = new LetterNode();
+            }
+            currentNode = currentNode.Alphabet[index];
+        }
+        currentNode.IsEnd = true;
+    }
+
+    public bool Search(string word)
+    {
+        return Dfs(word, root);
+    }
+
+    private bool Dfs(string target, LetterNode currentRoot)
+    {
+        if (target.Length == 0)
+        {
+            return currentRoot.IsEnd;
+        }
+
+        char firstLetter = target[0];
+        string remainingTarget = target.Substring(1);
+
+        if (firstLetter == '.')
+        {
+            for (int i = 0; i < 26; i++)
+            {
+                if (currentRoot.Alphabet[i] != null && Dfs(remainingTarget, currentRoot.Alphabet[i]))
+                {
+                    return true;
+                }
+            }
+        }
+        else
+        {
+            int index = firstLetter - 'a';
+            if (currentRoot.Alphabet[index] != null)
+            {
+                return Dfs(remainingTarget, currentRoot.Alphabet[index]);
+            }
+        }
+
+        return false;
+    }
+}