題目

中文：根據中序後序構建二叉樹

英文原題：
Given inorder and postorder traversal of a tree, construct the binary tree.
Note:
You may assume that duplicates do not exist in the tree.

For example, given

inorder = [9,3,15,20,7]
postorder = [9,15,7,20,3]

程式碼實現

實現方法類似給定前序中序構建二叉樹的方法：劍指offer–前序中序構建二叉樹

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def buildTree(self, inorder, postorder):
        """
        :type inorder: List[int]
        :type postorder: List[int]
        :rtype: TreeNode
        """
        if not inorder or not postorder:
            return None
        root = postorder[-1]
        index = inorder.index(root)
        ret = TreeNode(postorder.pop())
        ret.right = self.buildTree(inorder[index+1:], postorder)
        ret.left = self.buildTree(inorder[:index], postorder)
        return ret