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+# 1123. Lowest Common Ancestor of Deepest Leaves
+import leetcode
+
+"""
+given the 'root' of a binary tree, return the lowest common ancestor of its
+deepest leaves. recall that the node of a binary tree is a leaf if and only
+if it has no children, the depth of the root of the tree is 0. if the depth
+of a node is 'd', the depth of each of its children is 'd + 1'. and the
+lowest common ancestor of a set 's' is the node 'a' with the largest depth
+such that every node in 's' is in the subtree with root 'a'.
+"""
+
+
+class Solution(object):
+ def lcaDeepestLeaves(self, root):
+ """
+ :type root: Optional[TreeNode]
+ :rtype: Optional[TreeNode]
+ """
+
+ def depth(node):
+ if not node:
+ return 0
+ return max(depth(node.left), depth(node.right)) + 1
+
+ def dfs(node, m, n):
+ if not node:
+ return None
+ if m - 1 == n:
+ return node
+ l = dfs(node.left, m, n + 1)
+ r = dfs(node.right, m, n + 1)
+ if l and r:
+ return node
+ return l if l else r
+
+ m = depth(root)
+ return dfs(root, m, 0)
+
+
+if __name__ == "__main__":
+ obj = Solution()
+ r1 = leetcode.treenode_build(root=[3, 5, 1, 6, 2, 0, 8, None, None, 7, 4])
+ r2 = leetcode.treenode_build(root=[1])
+ r3 = leetcode.treenode_build(root=[0, 1, 3, None, 2])
+ print(obj.lcaDeepestLeaves(r1))
+ print(obj.lcaDeepestLeaves(r2))
+ print(obj.lcaDeepestLeaves(r3))