# Leetcode 1218 Solution

https://leetcode.com/problems/lowest-common-ancestor-of-deepest-leaves

## Solution

``````# 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 lcaDeepestLeaves(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
max_depth = 0
max_depth_nodes = set()

def dfs(node, depth=0):
nonlocal max_depth
nonlocal max_depth_nodes

if not node:
return

if depth > max_depth:
max_depth = depth
max_depth_nodes = {node}
elif depth == max_depth:

dfs(node.left, depth + 1)
dfs(node.right, depth + 1)

dfs(root)

ans = None
def find(node):
nonlocal max_depth_nodes
nonlocal ans

if not node:
return 0

left_cnt = find(node.left)
right_cnt = find(node.right)

if left_cnt > 0 and right_cnt > 0 and left_cnt + right_cnt == len(max_depth_nodes):
ans = node
elif left_cnt == 0 and right_cnt == 0 and node in max_depth_nodes and len(max_depth_nodes) == 1:
ans = node

return int(node in max_depth_nodes) + left_cnt + right_cnt

find(root)

return ans
``````