/************************************************************************/
        /*       35:     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.
         * */
        
        //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 minDepth(TreeNode root)        {             if (root == null)             {                 return 0;             }             if (root.left==null                     &&root.right==null                     )                 {                     return 1;                 }             int a=minDepth(root.left);             int b=minDepth(root.right);             if(a>0&&b>0)             {                 return Math.min(a, b)+1;             }             return a+b+1;                        }

35: Minimum Depth of Binary Tree