剑指offer 重建二叉树

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重建二叉树

题目

输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。

方法

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# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # 返回构造的TreeNode根节点
    def reConstructBinaryTree(self, pre, tin):
        # write code here
        """
        pre: root (preorder of left branch) (preorder of right or branch)
        tin: (inorder of left branch) root (inorder of left branch)
        """
        if not pre:
            return
        root=TreeNode(pre[0])
        i=tin.index(pre[0])
        root.left=self.reConstructBinaryTree(pre[1:i+1],tin[:i])
        root.right=self.reConstructBinaryTree(pre[i+1:],tin[i+1:])
        return root