Largest Value on Each Tree Level

Medium

You are given the root of a binary tree. A level is the set of nodes at the same distance from the root: the root is level 0, its children are level 1, and so on. Return a list whose i-th entry is the largest value among the nodes on level i. For an empty tree, return an empty list.

Example 1

root=tree_node([4, 9, 2, -3, None, 7, 1]) → [4, 9, 7]

Depth 0 holds only 4; depth 1 holds 9 and 2, so 9; depth 2 holds -3, 7 and 1, so 7.

Example 2

root=tree_node([-5, None, -8]) → [-5, -8]

Each level has a single node, so that node is the level's maximum.

Example 3

root=tree_node([]) → []

Constraints

The tree has between 0 and 10⁴ nodes
-2³¹ ≤ node value ≤ 2³¹ − 1

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Topics

Tree Depth-First Search Breadth-First Search Binary Tree

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The Tree Seen From the Right Medium Tree Columns, Top Down Medium First Value on the Lowest Row Medium Insert a Tree Level Medium A Tree Drawn on a Grid Medium

Input

root=tree_node([4, 9, 2, -3, None, 7, 1])

Expected

[4, 9, 7]

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