Construct Binary Tree from Preorder and Inorder Traversal Solution

Author: jinbeom

construct-binary-tree-from-preorder-and-inorder-traversal/kayden.py

@@ -0,0 +1,31 @@
+# 시간복잡도: O(N)
+# 공간복잡도: O(N)
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+
+
+class Solution:
+    def buildTree(self, preorder: List[int], inorder: List[int]) -> Optional[TreeNode]:
+
+        mapping = {}
+
+        for i in range(len(inorder)):
+            mapping[inorder[i]] = i
+
+        preorder = collections.deque(preorder)
+
+        def build(start, end):
+            if start > end: return None
+
+            root = TreeNode(preorder.popleft())
+            mid = mapping[root.val]
+
+            root.left = build(start, mid - 1)
+            root.right = build(mid + 1, end)
+
+            return root
+
+        return build(0, len(preorder) - 1)