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.
Solution:
1. /*
2. * Definition for a binary tree node.
3. * public class TreeNode {
4. * int val;
5. * TreeNode left;
6. * TreeNode right;
7. * TreeNode(int x) { val = x; }
8. * }
9. /
10. public class Solution {
11. public int minDepth(TreeNode root) {
12. if (root == null)
13. return 0;
14. 15. if (root.left == null)
16. return 1 + minDepth(root.right);
17. 18. if (root.right == null)
19. return 1 + minDepth(root.left);
20. 21. return 1 + Math.min(minDepth(root.left), minDepth(root.right));
22. }
23. }