From 97eb6f9759f08484a9e0b52a458dc61c3e24cdad Mon Sep 17 00:00:00 2001
From: ChaedongIm <chaedong.im.dev@gmail.com>
Date: Sun, 22 Dec 2024 12:35:55 +0900
Subject: [PATCH] =?UTF-8?q?feat:=20add=20Solution=20for=20=EC=B5=9C?=
 =?UTF-8?q?=EC=A0=81=ED=99=94?=
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---
 .../Chaedie.py                                | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/construct-binary-tree-from-preorder-and-inorder-traversal/Chaedie.py b/construct-binary-tree-from-preorder-and-inorder-traversal/Chaedie.py
index 7432a4100..8587dd26a 100644
--- a/construct-binary-tree-from-preorder-and-inorder-traversal/Chaedie.py
+++ b/construct-binary-tree-from-preorder-and-inorder-traversal/Chaedie.py
@@ -27,3 +27,31 @@ def buildTree(self, preorder: List[int], inorder: List[int]) -> Optional[TreeNod
         newNode.right = self.buildTree(preorder[mid + 1 :], inorder[mid + 1 :])
 
         return newNode
+
+'''
+알고달레 참고해서 최적화 진행했습니다.
+1) 시간복잡도 최적화: dictionary 를 활용해 mid 를 찾는 index 메서드 제거
+2) 공간복잡도 최적화: preorder, inorder 배열을 넘기는것이 아닌 index 만 넘김
+
+Time: O(n)
+Space: O(n)
+
+'''
+
+class Solution:
+    def buildTree(self, preorder: List[int], inorder: List[int]) -> Optional[TreeNode]:
+        indices = { val: idx for idx, val in enumerate(inorder) }
+        pre_iter = iter(preorder)
+
+        def dfs(start, end):
+            if start > end:
+                return None
+            
+            val = next(pre_iter)
+            mid = indices[val]
+
+            left = dfs(start, mid - 1)
+            right = dfs(mid + 1, end)
+            return TreeNode(val, left, right)
+
+        return dfs(0, len(inorder) - 1)