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  • [LeetCode]题解(python):102 Binary Tree Level Order Traversal

    题目来源


    https://leetcode.com/problems/binary-tree-level-order-traversal/

    Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).


    题意分析


    Input: 一个二叉树

    Output:一个每层数值组合的list

    Conditions:层次遍历


    题目思路


    采用dfs,先序遍历的方法,采用一个level值来记录高度,注意要适时扩充list的size


    AC代码(Python)

     1 # Definition for a binary tree node.
     2 # class TreeNode(object):
     3 #     def __init__(self, x):
     4 #         self.val = x
     5 #         self.left = None
     6 #         self.right = None
     7 
     8 class Solution(object):
     9     def preorder(self, root, level, res):
    10         if root:
    11             if len(res) < level + 1: res.append([])
    12             res[level].append(root.val)
    13             self.preorder(root.left, level + 1, res)
    14             self.preorder(root.right, level + 1, res)
    15     def levelOrder(self, root):
    16         """
    17         :type root: TreeNode
    18         :rtype: List[List[int]]
    19         """
    20         res = []
    21         self.preorder(root, 0, res)
    22         print res
    23         return res
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  • 原文地址:https://www.cnblogs.com/loadofleaf/p/5502285.html
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