求解二叉树的最短路径

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

    public int run(TreeNode root) {

        if(root == null) return 0;

        if(root.left == null && root.right != null){

          return run(root.right) + 1;

        }

        if(root.left != null && root.right == null){

            return run(root.left) + 1;

        }

        return Math.min(run(root.left),run(root.right))+1;

    }

}