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。
思路:1、从前序遍历中找到根节点,并找到根节点在中序遍历的下标i
2、按照i的值分割前序和中序
3、递归1~2
# -*- 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
if not pre or not tin:
return None
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