< Previous
Next >
Given a binary tree where every node has a unique value, and a target key k
, find the value of the nearest leaf node to target k
in the tree.
Here, nearest to a leaf means the least number of edges travelled on the binary tree to reach any leaf of the tree. Also, a node is called a leaf if it has no children.
In the following examples, the input tree is represented in flattened form row by row.
The actual root
tree given will be a TreeNode object.
Example 1:
Input:
root = [1, 3, 2], k = 1
Diagram of binary tree:
1
/ \
3 2
Output: 2 (or 3)
Explanation: Either 2 or 3 is the nearest leaf node to the target of 1.
Example 2:
Input:
root = [1], k = 1
Output: 1
Explanation: The nearest leaf node is the root node itself.
Example 3:
Input:
root = [1,2,3,4,null,null,null,5,null,6], k = 2
Diagram of binary tree:
1
/ \
2 3
/
4
/
5
/
6
Output: 3
Explanation: The leaf node with value 3 (and not the leaf node with value 6) is nearest to the node with value 2.
Note:
root
represents a binary tree with at least 1
node and at most 1000
nodes.
- Every node has a unique
node.val
in range [1, 1000]
.
- There exists some node in the given binary tree for which
node.val == k
.
[Tree]
Hints
Hint 1
Convert the tree to a general graph, and do a breadth-first search. Alternatively, find the closest leaf for every node on the path from root to target.