102. 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).

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

    3
   / \
  9  20
    /  \
   15   7

 

return its level order traversal as:

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

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

class Solution(object):
    def levelOrder(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        rlist=[]
        if root==None:
            return rlist
        q=Queue.Queue()
        q.put(root)
        while q.empty()!=True:
            count=q.qsize()
            sublist=[]
            for i in range(count): 
                x=q.get()
                sublist.append(x.val)
                if x.left!=None: q.put(x.left)
                if x.right!=None: q.put(x.right)
            rlist.append(sublist)
        return rlist   

 

# 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 root ==None:
            return []
        rlist=[]
        nodelist=[root]
        while nodelist!=[]:
            sublist=[l.val for l in nodelist if l]
            templist=[]
            for i in nodelist:
                if i!=None:
                    if i.left:templist.append(i.left)
                    if i.right:templist.append(i.right)
            nodelist= templist  
            rlist.append(sublist)
        return rlist