首页 > itarticle > PU Binary Tree Level Order Traversal

PU Binary Tree Level Order Traversal

admin 11月 12, 2020 0

Jan 01, 1970

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

For example:

Given binary tree [3,9,20,null,null,15,7],

return its level order traversal as:

[
  [3],
  [9,20],
  [15,7]
]

Python Solution:

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def levelOrder(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        if not root: return []
        res = []
        l = [root]
        while l:
            r = []
            vals = []
            for node in l:
                vals.append(node.val)
                if node.left: r.append(node.left)
                if node.right: r.append(node.right)
            res.append(vals)
            l = r
        return res

Summary:

This should be a easy problem.

LeetCode: 102. Binary Tree Level Order Traversal