题目:
二叉树的层次遍历 II:给定一个二叉树,返回其节点值自底向上的层次遍历。 (即按从叶子节点所在层到根节点所在的层,逐层从左向右遍历)
思路:
正常层序遍历结果的逆输出。
程序:
# Definition for a binary tree node. # class TreeNode: # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution: def levelOrderBottom(self, root: TreeNode) -> List[List[int]]: if not root: return [] result = [] current_level = [root] while current_level: auxiliary = [] next_level = [] for node in current_level: auxiliary.append(node.val) if node.left: next_level.append(node.left) if node.right: next_level.append(node.right) result.append(auxiliary) current_level = next_level result.reverse() return result