/************************************************************************/
        /*       34:     Maximum Depth of Binary Tree                                        */
        /************************************************************************/
        /*
         * Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
         * */
      //求根节点到叶子节点的最短路径 递归
        // 左边或者右边没有叶子节点时，需要特殊处理

public int maxDepth(TreeNode root)        {                        if (root == null)            {                return 0;            }            if (root.left==null                    &&root.right==null                    )                {                    return 1;                }            int a=maxDepth(root.left);            int b=maxDepth(root.right);            if(a>0&&b>0)            {                return Math.max(a, b)+1;            }            return a+b+1;        }

34: Maximum Depth of Binary Tree