111. Minimum Depth of Binary Tree

/** * 111.Minimum Depth of Binary Tree  * * Problem 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. * * Definition for a binary tree node. * 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) return minDepth(root.right) + 1;          if(root.right == null) return minDepth(root.left) + 1;          return Math.min(minDepth(root.left), minDepth(root.right)) + 1;      }}