【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】

    public static ArrayList<LinkedList<Node>> findLevelLinkList(Node root)
    {
        int level = 0;
        ArrayList<LinkedList<Node>> result = 
                new ArrayList<LinkedList<Node>>();
        LinkedList<Node> list = new LinkedList<Node>();
        
        list.add(root);
        result.add(level, list);
        
        while(true)
        {
            list = new LinkedList<Node>();
            for(int i=0;i< result.get(level).size();i++)
            {
                Node n = result.get(level).get(i);
                if(n!=null)
                {
                    if(n.left!=null) 
                        list.add(n.left);
                    if(n.right!=null)
                        list.add(n.right);
                }
            }
            if(list.size() >0)
                result.add(level+1, list);
            else
                break;
            level++;
        }
        return result;
    }