题解 | #求二叉树的层序遍历#

using System;
using System.Collections.Generic;

/*
public class TreeNode
{
	public int val;
	public TreeNode left;
	public TreeNode right;

	public TreeNode (int x)
	{
		val = x;
	}
}
*/

class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型二维数组
     */
    public List<List<int>> levelOrder (TreeNode root) {
        // write code here
        List<List<int>> result = new List<List<int>>();
        if(root==null)
        return result;
        Queue<TreeNode> queue = new Queue<TreeNode>();
        queue.Enqueue(root);
        while(queue.Count>0)
        {
            List<int> thisList = new List<int>();
            int len = queue.Count;
            for(int i =0;i<len;i++)
            {
                TreeNode node = queue.Dequeue();
                if(node.left!=null) queue.Enqueue(node.left);
                if(node.right!=null) queue.Enqueue(node.right);
                thisList.Add(node.val);
                
            }
            result.Add(thisList);
        }
        return result;
    }
}