LevelOrderTraversal2.py

from typing import List, Optional
from BinaryTree import TreeNode, BinaryTree

class Solution:
    def levelOrderBottom(self, root: Optional[TreeNode]) -> List[List[int]]:
        if root == None:
            return []
        if root.left == None and root.right == None:
            return [[root.val]]
        returnList = self.find_bottom_and_return([root])
        returnList.append([root.val])
        return returnList
        


    def find_bottom_and_return(self, queue: List[TreeNode]) -> List[List]:
        if(len(queue) == 0):
            return []
        newQueue = []
        for i in range(0, len(queue)):
            if queue[i].left != None:
                newQueue.append(queue[i].left)

            if queue[i].right != None:
                newQueue.append(queue[i].right)
        bottom = self.find_bottom_and_return(newQueue)
        if len(newQueue) == 0:
            return bottom
        newQueue = list(map(lambda element : element.val, newQueue))
        bottom.append(newQueue)
        return bottom
    
    def levelOrderUsingLoop(self, root: Optional[TreeNode]) -> List[List[int]]:
        if root == None:
            return []
        queue = [root]
        levels = [[root.val]]
        while(len(queue) != 0):
            currentList = []
            for i in range(0,len(queue)):
                element = queue.pop(0)
                if element.left:
                    currentList.append(element.left.val)
                    queue.append(element.left)
                if element.right:
                    currentList.append(element.right.val)
                    queue.append(element.right)
            if len(currentList) != 0:        
                levels.insert(0, currentList)
        return levels             

              
    

bt = BinaryTree()
root = bt.create_tree_from_array([3,9,20,None,None,15,7])
reverse_level_order = Solution().levelOrderBottom(root)
print(reverse_level_order)
print(Solution().levelOrderUsingLoop(root))