# Definition for a binary tree node.
class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

class Solution:
    
    def __init__(self):
        self.levels = dict()
    
    def maxLevelSum(self, root):
        # recursively add sums for all nodes to hashmap with key as level
        self.traverseWithLevel(root, 1)
        
        maximum = -1
        maxLvl = 1
        for key, value in self.levels.items():
            if value > maximum:
                maxLvl = key
                maximum = value
                
        return maxLvl
    
    def traverseWithLevel(self, tree, level):
        if tree is None:
            return
        
        if level not in self.levels:
            self.levels[level] = 0
            
        self.levels[level] += tree.val
        self.traverseWithLevel(tree.left, level + 1)
        self.traverseWithLevel(tree.right, level + 1)


s = Solution()
print("Expected: 2")
tree = TreeNode(1)
tree.right = TreeNode(2)
tree.left = TreeNode(3)
print("Got:", s.maxLevelSum(tree))