Minimum Depth of Binary Tree
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
3
/ \
9 20
/ \
15 7Input
root = [3,9,20,null,null,15,7]Output
2The shortest path from the root to a nearest leaf contains 2 nodes.
Example 2
2
\
3
\
4
\
5
\
6Input
root = [2,null,3,null,4,null,5,null,6]Output
5The only leaf is node 6, so the shortest path from the root contains 5 nodes.
Constraints
- The number of nodes in the tree is in the range
[0, 10^5]. -1000 <= Node.val <= 1000