【IT笔试面试题整理】给定二叉树，给每层生成一个链表

【试题描述】定义一个函数，给定二叉树，给每层生成一个链表

We can do a simple level by level traversal of the tree, with a slight modification of the breath-first traversal of the tree
In a usual breath first search traversal, we simply traverse the nodes without caring which level we are on In this case, it is critical to know the level We thus use a dummy node to indicate when we have finished one level and are starting on the next

【参考代码】

 1     public static ArrayList<LinkedList<Node>> findLevelLinkList(Node root)
 2     {
 3         int level = 0;
 4         ArrayList<LinkedList<Node>> result =
 5                 new ArrayList<LinkedList<Node>>();
 6         LinkedList<Node> list = new LinkedList<Node>();
 7
 8         list.add(root);
 9         result.add(level, list);
10
11         while(true)
12         {
13             list = new LinkedList<Node>();
14             for(int i=0;i< result.get(level).size();i++)
15             {
16                 Node n = result.get(level).get(i);
17                 if(n!=null)
18                 {
19                     if(n.left!=null)
20                         list.add(n.left);
21                     if(n.right!=null)
22                         list.add(n.right);
23                 }
24             }
25             if(list.size() >0)
26                 result.add(level+1, list);
27             else
28                 break;
29             level++;
30         }
31         return result;
32     }