feat: construct-binary-tree-from-preorder-and-inorder-traversal

Author: junbinding

Diff for: recs.construct-binary-tree-from-preorder-and-inorder-traversal.py

@@ -0,0 +1,29 @@
+from typing import List
+class TreeNode:
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+class Solution:
+    """
+    105. 从前序与中序遍历序列构造二叉树
+    https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/
+    根据一棵树的前序遍历与中序遍历构造二叉树。
+    前序遍历 preorder = [3,9,20,15,7]，根 + 左 + 右
+    中序遍历 inorder = [9,3,15,20,7]，左 + 根 + 右
+    """
+    def buildTree(self, preorder: List[int], inorder: List[int]) -> TreeNode:
+        if not preorder or not inorder:
+            return
+
+        # 找到根节点
+        root = TreeNode(preorder[0])
+        # 从中序列表中，通过根节点分割左右子树
+        idx = inorder.index(preorder[0])
+        root.left = self.buildTree(preorder[1:idx+1], inorder[:idx])
+        root.right = self.buildTree(preorder[1+idx:], inorder[idx+1:])
+
+        return root
+
+