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1123. Lowest Common Ancestor of Deepest Leaves (Medium)

Given a rooted 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, and if the depth of a node is d, the depth of each of its children is d+1.
• The lowest common ancestor of a set S of nodes is the node A with the largest depth such that every node in S is in the subtree with root A.

 

Example 1:

Input: root = [1,2,3]
Output: [1,2,3]
Explanation: 
The deepest leaves are the nodes with values 2 and 3.
The lowest common ancestor of these leaves is the node with value 1.
The answer returned is a TreeNode object (not an array) with serialization "[1,2,3]".

Example 2:

Input: root = [1,2,3,4]
Output: [4]

Example 3:

Input: root = [1,2,3,4,5]
Output: [2,4,5]

 

Constraints:

• The given tree will have between 1 and 1000 nodes.
• Each node of the tree will have a distinct value between 1 and 1000.

Related Topics

[Tree] [Depth-first Search]

Hints

Hint 1

Do a postorder traversal.

Hint 2

Then, if both subtrees contain a deepest leaf, you can mark this node as the answer (so far).

Hint 3

The final node marked will be the correct answer.