function Print(pRoot)
{
    // write code here
    //层序遍历二叉树
    var res= []
    var level = 0
    function BFS(node,level){
        if(node){
            if(!res[level]){
                res[level] = []
            }
            res[level].push(node.val)
            level+=1
            BFS(node.left,level)
            BFS(node.right,level)
        }
    }
    BFS(pRoot,level)
    return res
}