力扣-102、107 二叉树的层次遍历I、II

最新推荐文章于 2024-07-08 15:13:40 发布

想念@思恋

最新推荐文章于 2024-07-08 15:13:40 发布

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分类专栏： leetcode

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# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
# 解题关键--使用字典，记录每一层的节点；
		  #前序遍历的方法
# 102
class Solution:
    def levelOrder(self, root: TreeNode) -> List[List[int]]:
        if root == None:
            return []
        res = {}
        # queue = [root]
        layer = 0
        # 前序遍历
        def PreOrder(root, layer):
            if layer not in res:
                res[layer] = [root.val]
            else:
                res[layer].append(root.val)
            if root.left:
                PreOrder(root.left, layer+1)  
            if root.right:
                PreOrder(root.right, layer+1)
        InOrder(root, 0)
        res_ = []
        for k, v in res.items():
            res_.append(v)
        # print(res_)
        return res_

# 107
class Solution:
    def levelOrderBottom(self, root: TreeNode) -> List[List[int]]:
        if root == None:
            return []
        res = {}
        def Level(root, layer):
            if layer not in res:
                res[layer] = [root.val]
            else:
                res[layer].append(root.val)
            if root.left:
                Level(root.left, layer+1)
            if root.right:
                Level(root.right, layer+1)
        Level(root,1)
        r = []
        for k,v in res.items():
            r.append(v)
        return r[::-1]