Is Minimum Depth of Binary Tree easy or hard?

Minimum Depth of Binary Tree is classified as an Easy problem on most coding platforms. The challenge mainly involves recognizing that BFS naturally finds the nearest leaf and correctly handling edge cases when using DFS with nodes that have only one child.

Minimum Depth of Binary Tree Python/Java solution

Python and Java solutions typically implement either BFS using a queue or DFS using recursion. The BFS version uses a queue to track nodes and their depth, returning immediately when the first leaf is found. Both implementations run in O(n) time and are widely accepted in coding interviews and online judges.

How to solve Minimum Depth of Binary Tree in O(n)?

Traverse the tree once using either BFS or DFS. In BFS, push the root into a queue and process nodes level by level until you encounter the first leaf node, then return the depth. In DFS, recursively compute the depth of left and right subtrees while carefully handling nodes with only one child. Both strategies visit each node once, resulting in O(n) time complexity.

What is the best approach for Minimum Depth of Binary Tree?

Breadth-first search (BFS) is generally the best approach. BFS traverses the tree level by level, so the first leaf node encountered is guaranteed to represent the minimum depth. This allows early termination without exploring deeper levels. The time complexity is O(n) and the space complexity is O(n) in the worst case.

Is Minimum Depth of Binary Tree asked at Google/Amazon/Meta?

Minimum depth and other binary tree traversal problems appear frequently in interviews at companies such as Amazon, Google, and Meta. Interviewers use it to test understanding of tree traversal strategies, recursion, and BFS level-order processing. Variations of tree depth problems are common in coding rounds.

What data structure is used in Minimum Depth of Binary Tree?

The primary data structure is a binary tree. The BFS solution additionally uses a queue to process nodes level by level, while the DFS solution uses recursion or an explicit stack. Both approaches rely on tree traversal techniques.

What is the time complexity of Minimum Depth of Binary Tree?

The time complexity is O(n) because every node may need to be visited once in the worst case. Both BFS and DFS solutions traverse the tree nodes exactly once. The difference lies in space usage: BFS may use O(n) queue space while DFS typically uses O(h) recursion stack space.

Description Solution Video 11:50

111. Minimum Depth of Binary Tree

Easy53.7% acceptance7 companies

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

Note: A leaf is a node with no children.

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: 2

Example 2:

Input: root = [2,null,3,null,4,null,5,null,6]
Output: 5

Constraints:

The number of nodes in the tree is in the range [0, 10⁵].
-1000 <= Node.val <= 1000

Asked at 7 companies

Livspace

TCS Bloomberg

Google Amazon Microsoft Meta

Topics

11:50

Still stuck?Read 4 approaches, or watch a walkthrough.

Open solution

111. Minimum Depth of Binary Tree

Asked at 7 companies

Topics

Similar problems