Leetcode：111. Minimum Depth of Binary Tree（求Tree的最小的深度）

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.
给定一个二叉树，找到它的最小深度。
最小深度是沿着从根节点到最近的叶节点的最短路径的节点的数量。
很Easy。
代码：

public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int x) { val = x; }
    }

    class Solution {
        public int minDepth(TreeNode root) {
            if (root==null) {
                return 0;
            }

            int left = minDepth(root.left);
            int right = minDepth(root.right);
            if (left==0||right==0) {
                return left+right+1;
            }
            return Math.min(left,right) + 1;
        }
    }

或者

    public int minDepth(TreeNode root) {
 if (root==null) {
                    return 0;
                }
            if (root.left == null)   
                 return minDepth(root.right) + 1;  
             else if (root.right == null)   
                 return minDepth(root.left) + 1;  
             else   
                 return Math.min(minDepth(root.left), minDepth(root.right)) + 1;  
    }