leetcode Minimum Depth of Binary Tree

/**
 * 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&&root.right!=null){
            return 1+Math.min(minDepth(root.left), minDepth(root.right));
        }
        if(root.left!=null){
            return 1+minDepth(root.left);
        }
        if(root.right!=null){
            return 1+minDepth(root.right);
        }
        return 0;
    }
}