binary-tree-level-order-traversal

##Binary Tree Level Order Traversal

leetcode: 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).

class Solution:

# @return a list of lists of integers
def levelOrder(self, root):
    #list to save integers
    if not root:
        return []
    result = []
    # a recu 
    self.helper(root, 0, result)
    return result

def helper(self, root, level, result):
    #
    if not root:
        return
    if level+1 > len(result):
            result.append([])
    result[level].append(root.val)
    self.helper(root.left, level+1, result)
    self.helper(root.right, level+1, result)