LeetCode 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.

 1 /**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int minDepth(TreeNode root) {
        if (root == null) {
            return 0;
        }
        
        if (root.left==null &&root.right==null) {
            return 1;
        }
        if (root.left==null) {
            return 1+minDepth(root.right);
        }
        if (root.right==null) {
            return 1+minDepth(root.left);
        }
        return 1+Math.min(minDepth(root.left), minDepth(root.right));
    }
}