Description
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. A leaf is a node with no children.
Examples
Input:
root = [3,9,20,null,null,15,7]Output:
2Explanation:
Shortest path is 3→9.
Input:
root = [1]Output:
1Explanation:
The tree has only one node (the root), which is also a leaf. The minimum depth is 1.
Input:
root = [5,3,8,1,null,7,12]Output:
3Explanation:
The tree has leaves at depths 3 (nodes 1, 7, 12). The shortest path from root to any leaf is 5→3→1 or 5→8→7 or 5→8→12, all with depth 3.
Constraints
- •
0 ≤ nodes ≤ 10⁵