Leetcode889.py

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


class Solution:
    def constructFromPrePost(self, pre, post):
        """
        :type pre: List[int]
        :type post: List[int]
        :rtype: TreeNode
        """
        if not pre: return
        root = TreeNode(pre[0])
        pre, post = pre[1:], post[:-1]
        if not pre: return root
        i = post.index(pre[0])
        root.left = self.constructFromPrePost(pre[:i + 1], post[:i + 1])
        root.right = self.constructFromPrePost(pre[i + 1:], post[i + 1:])
        return root

test_pre = [1,2,4,5,3,6,7]
test_post = [4,5,2,6,7,3,1]
S = Solution()
x = S.constructFromPrePost(pre=test_pre,post=test_post)