102. Binary Tree Level Order Traversal

[Shawngbk]

/**

• Definition for a binary tree node.
• public class TreeNode {
• int val;
• TreeNode left;
• TreeNode right;
• TreeNode(int x) { val = x; }
• } */

public class Solution { public List<List> levelOrder(TreeNode root) { List<List> list = new LinkedList<List>(); if(root == null) return list; //创建一个队列，用于存放所有节点 Queue curLevel = new LinkedList(); curLevel.add(root); while(!curLevel.isEmpty()) { //创建一个List记录当前层所有节点值 int size = curLevel.size(); List curList = new LinkedList(); for(int i = 0; i<size; i++) { //poll()获取并移除此列表的头结点 TreeNode curNode = curLevel.poll(); curList.add(curNode.val); //记录每一层的节点值到List中 if(curNode.left != null) { curLevel.offer(curNode.left); } if(curNode.right != null) { curLevel.offer(curNode.right); } } //将当前List添加到List<List>中 list.add(curList); } return list; } }

[Shawngbk]

Amazon