107. 二叉树的层次遍历 II

https://leetcode-cn.com/problems/binary-tree-level-order-traversal-ii/description/

package com.test;import java.util.ArrayList;import java.util.List;/** * @Author stono * @Date 2018/8/27 上午10:40 */public class Lesson107 {    public static void main(String[] args) {        TreeNode t1 = new TreeNode(1);        TreeNode t2L = new TreeNode(2);        TreeNode t2R = new TreeNode(2);        TreeNode t3_1 = new TreeNode(3);        TreeNode t3_2 = new TreeNode(4);        TreeNode t3_3 = new TreeNode(4);        TreeNode t3_4 = new TreeNode(3);        t1.left = t2L;        t1.right = t2R;        t2L.left = t3_1;        t2L.right = t3_2;        t2R.left = t3_3;        t2R.right = t3_4;        List
     
      
       > lists = levelOrderBottom(t1);        System.out.println(lists);    }    public static List
       
        
         > levelOrderBottom(TreeNode root) {        List
         
          
           > res = new ArrayList<>(); if (root == null) { return res; } List
           
             list = new ArrayList<>(8); list.add(root.val); TreeNode leftNode = root.left; TreeNode rightNode = root.right; List
            
              nodes = new ArrayList<>(); nodes.add(leftNode); nodes.add(rightNode); // 进行递归累加 levelOrderBottom(res, nodes); res.add(list); return res; } private static void levelOrderBottom(List
             
              
               > res, List
               
                 nodes) { List
                
                  list = new ArrayList<>(8); List
                 
                   nodes2 = new ArrayList<>(); for (TreeNode node : nodes) { if (node != null) { list.add(node.val); nodes2.add(node.left); nodes2.add(node.right); } } // 如果遍历结果中包含了多个数字 if (list.size() > 0) { levelOrderBottom(res, nodes2); res.add(list); } }}