leetcode 1302 - deepest leaves sum.py

# deepest leaves sum | leetcode 1302 | https://leetcode.com/problems/deepest-leaves-sum/
# method: dfs

# 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 deepestLeavesSum(self, root) -> int:
        result = 0
        maxHeight = 0
        
        # dfs
        def dfs(node, currHeight):
            nonlocal result, maxHeight
            if node is None:
                return
            
            # reset if current height is not max
            if currHeight > maxHeight:
                result = 0
                maxHeight = currHeight
           
            # add to sum if current height is max
            if currHeight == maxHeight:
                result += node.val
               
            # recursively traverse left and right subtrees
            dfs(node.left, currHeight + 1)
            dfs(node.right, currHeight + 1)
            
        dfs(root, 0)
        return result