Leftmost Deepest Node Value

BronzeShow difficulty

10000ms500MBSep 24, 2026

You are given the root of a binary tree, root. Return the value of its deepest node, where the root has depth 0.

If more than one node is at the maximum depth, return the leftmost one: the node that comes first when that depth's nodes are listed left to right, in the same order as a level-order traversal.

Tree Encoding

Your function receives root as a TreeNode. The node type is provided for you, with val, left, and right fields.

The examples below write the tree as its level-order traversal, where null marks a missing child of a listed node and trailing nulls are omitted. That is only how the input is displayed; the decoding is done for you.

Constraints

The number of nodes in root is in the range $[1, 10^5]$ .
$-10^9 \leq$ Node.val $\leq 10^9$

Examples

Example 1

Input

root = [1, 2, 3, 4, 5, null, 6]

root

Output

Explanation

The deepest level is depth 2, holding `4`, `5`, and `6` in left-to-right order. The leftmost of them is `4`.

Example 2

Input

root = [1, 2, 3, null, null, 4, 5]

root

Output

Explanation

Node `2` has no children, so the deepest level (depth 2) only comes from `3`'s subtree: `4` and `5`. The leftmost is `4`.

Example 3

Input

root = [1]

root

Output

Explanation

The single node `1` is its own deepest node.

Loading editor...

Samples 3

Custom 0

sample

Include in Run

root =tree

Expected

Leftmost Deepest Node Value

BronzeShow difficulty

10000ms500MBSep 24, 2026

You are given the root of a binary tree, root. Return the value of its deepest node, where the root has depth 0.

If more than one node is at the maximum depth, return the leftmost one: the node that comes first when that depth's nodes are listed left to right, in the same order as a level-order traversal.

Tree Encoding

Your function receives root as a TreeNode. The node type is provided for you, with val, left, and right fields.

Constraints

The number of nodes in root is in the range $[1, 10^5]$ .
$-10^9 \leq$ Node.val $\leq 10^9$

Examples

Example 1

Input

root = [1, 2, 3, 4, 5, null, 6]

root

Output

Explanation

The deepest level is depth 2, holding `4`, `5`, and `6` in left-to-right order. The leftmost of them is `4`.

Example 2

Input

root = [1, 2, 3, null, null, 4, 5]

root

Output

Explanation

Node `2` has no children, so the deepest level (depth 2) only comes from `3`'s subtree: `4` and `5`. The leftmost is `4`.

Example 3

Input

root = [1]

root

Output

Explanation

The single node `1` is its own deepest node.

Loading editor...

Samples 3

Custom 0

sample

Include in Run

root =tree

Expected