Linked list focus problem, a lot of polygon, consider intersect disjoint, ring without ring + Find Leaves of Binary Tree (Java)

Break the loop at the last node which pointed to the entry.

Given a binary tree, collect a tree ' s nodes as if you were doing this:collect and remove all leaves, repeat until the Tre E is empty.

Example:
Given binary Tree

          1         /         2   3       /\           4   5    

Returns [4, 5, 3], [2], [1].

ollowup: Each node still has a left,right pointer, but the structure is not a tree, but graph how to calculate, consider there is/no circular dependency two kinds of situations;the method is to record the calculated node level and a set record with HashMap dependent node

Public list<list<integer>> findleaves (TreeNode root) {    list<list<integer>> result = new Arraylist<list<integer>> ();    Helper (result, root);    return result;} Traverse the tree bottom-up recursivelyprivate int helper (list<list<integer>> List, TreeNode root) {    if (root==null)        return-1;     int left = helper (list, root.left);    int right = Helper (list, root.right);    int curr = Math.max (left, right) +1;     The first time this code is reached was when curr==0,    //since The tree was bottom-up processed.    if (List.size () <=curr) {        list.add (new arraylist<integer> ());    }     List.get (Curr). Add (root.val);     return Curr;}

　　

Linked list focus problem, a lot of polygon, consider intersect disjoint, ring no ring + Find Leaves of Binary Tree (Java)