#1123
Lowest Common Ancestor of Deepest Leaves
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hash table · tree · depth-first search · breadth-first search · binary tree
Description
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.
- 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 = [3,5,1,6,2,0,8,null,null,7,4]
Output: [2,7,4]
Explanation: We return the node with value 2, colored in yellow in the diagram.
The nodes coloured in blue are the deepest leaf-nodes of the tree.
Note that nodes 6, 0, and 8 are also leaf nodes, but the depth of them is 2, but the depth of nodes 7 and 4 is 3.
Example 2:
Input: root = [1]
Output: [1]
Explanation: The root is the deepest node in the tree, and it's the lca of itself.
Example 3:
Input: root = [0,1,3,null,2]
Output: [2]
Explanation: The deepest leaf node in the tree is 2, the lca of one node is itself.
Solution