重建二叉树

重建二叉树

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Time    : 2018/7/29 19:39
# @File    : # 007.py
# @Software: PyCharm
# @Author  : wxw
# @Contact : [email protected]
# @Desc    : 重建二叉树

"""
preOrder{1,2,4,7,3,5,6,8}和midOrder{4,7,2,1,5,3,8,6}
"""

class TreeNode:
    def __init__(self, value, left=None, right=None):
        self.value = value
        self.left = left
        self.right = right

def Construct(pre, tin):
    if len(pre) == 0:
        return None
    if len(pre) == 1:
        return TreeNode(pre[0])
    root = TreeNode(pre[0])
    idx = tin.index(pre[0])
    root.left = Construct(pre[1:idx+1], tin[:idx])
    root.right = Construct(pre[idx+1:], tin[idx+1:])
    return root

先序遍历: 第一个节点为根节点;
中序遍历: 根节点在中间位置,两边分别为左子树和右子树.