4.4 Given a binary tree, design an algorithm which creates a linked list of all the nodes at each depth (e.g., if you have a tree with depth D, you‘ll have D linked lists).
[CareerCup] 4.4 Create List at Each Depth of Binary Tree 二叉树的各层创建链表
原文：http://www.cnblogs.com/grandyang/p/4694887.html