/**
* Definition for a binary tree node.
* public class TreeNode {
* public int val;
* public TreeNode left;
* public TreeNode right;
* public TreeNode(int x) { val = x; }
* }
*/
public class Solution {
//二叉树层序遍历（广度优先搜索） private List<TreeNode> GetNext(List<TreeNode> nodes)
{
var list = new List<TreeNode>(); foreach (var node in nodes)
{
if (node.left != null)
{
list.Add(node.left);
}
if (node.right != null)
{
list.Add(node.right);
}
}
return list;
} public IList<IList<int>> LevelOrderBottom(TreeNode root)
{
var list = new List<IList<int>>(); if (root != null)
{
var rootlist = new List<TreeNode>();
rootlist.Add(root); var nlist = new List<int>();
nlist.Add(root.val);
list.Add(nlist); while (rootlist.Count > )
{
rootlist = GetNext(rootlist); var xlist = new List<int>();
foreach (var r in rootlist)
{
xlist.Add(r.val);
}
if (xlist.Any())
{
list.Add(xlist);
}
}
list.Reverse();
}
return list; }
}
https://leetcode.com/problems/binary-tree-level-order-traversal-ii/#/description