Is Find the Level of Tree with Minimum Sum easy or hard?

This problem is generally considered medium difficulty. The main challenge is recognizing that a level-order traversal cleanly separates nodes by depth, allowing straightforward computation of sums for each level.

Find the Level of Tree with Minimum Sum Python/Java solution

Most implementations use a queue-based BFS traversal. Python typically uses collections.deque, while Java uses a Queue or LinkedList to store nodes level by level. The algorithm calculates the sum for each level and keeps track of the level with the smallest sum.

How to solve Find the Level of Tree with Minimum Sum in O(n)?

Traverse the tree using a queue for level-order traversal. For each level, iterate through all nodes currently in the queue, compute their total sum, and push their children into the queue. Track the smallest level sum encountered and the corresponding level index. Since each node is processed once, the algorithm runs in O(n).

What is the best approach for Find the Level of Tree with Minimum Sum?

Breadth-First Search (level order traversal) is the best approach. It processes the binary tree one level at a time using a queue and computes the sum of node values for each level. Since every node is visited exactly once, the algorithm runs in O(n) time and naturally groups nodes by level.

Is Find the Level of Tree with Minimum Sum asked at Google/Amazon/Meta?

Tree traversal problems that involve computing values per level are common in interviews at companies like Google, Amazon, and Meta. Variants such as maximum level sum, average of levels, and level-based aggregations frequently appear in coding interviews to test BFS and binary tree understanding.

What data structure is used in Find the Level of Tree with Minimum Sum?

The primary data structure is a queue used for Breadth-First Search traversal of the binary tree. The queue allows nodes to be processed level by level. In DFS variants, an array or hash map is also used to store cumulative sums for each depth.

What is the time complexity of Find the Level of Tree with Minimum Sum?

The optimal solution runs in O(n) time where n is the number of nodes in the tree. Each node is visited once during traversal. The space complexity is O(w) for BFS where w is the maximum width of the tree, or O(h) for a DFS solution where h is the tree height.

Description Hints 2 Solution Video 5:13

3157. Find the Level of Tree with Minimum Sum

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Given the root of a binary tree root where each node has a value, return the level of the tree that has the minimum sum of values among all the levels (in case of a tie, return the lowest level).

Note that the root of the tree is at level 1 and the level of any other node is its distance from the root + 1.

Example 1:

Input: root = [50,6,2,30,80,7]

Output: 2

Explanation:

Example 2:

Input: root = [36,17,10,null,null,24]

Output: 3

Explanation:

Example 3:

Input: root = [5,null,5,null,5]

Output: 1

Explanation:

Constraints:

The number of nodes in the tree is in the range [1, 10⁵].
1 <= Node.val <= 10⁹

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Microsoft

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Hint 1

Run a DFS on the tree and update an array sum where sum[i] is the sum for level i.

Hint 2

The answer is the first minimum element of sum.

5:13

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3157. Find the Level of Tree with Minimum Sum

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