[Leetcode] Minimum Depth of Binary Tree

Problem

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.

Analysis

• Recursive calculate the depth of the tree
• 1 + Math.min(left-tree, right-tree)
• Need to deal with the case when left-tree or right-tree is null
• If left-tree is null, return right-tree
• If right-tree is null, return left-tree
• Time: O(n)
• As it traverses each node once

Code