leetcode讲解--515. Find Largest Value in Each Tree Row

题目You need to find the largest value in each row of a binary tree.Example:Input: 1 / \ 3 2 / \ \ 5 3 9 Output: [1, 3, 9]讲解又是树的层次遍历题。相同的题我已经做了两个了：637. Average of Levels in Binary Tree、429. N-ary Tree Level Order TraversalJava代码/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */class Solution { List<Integer> result = new ArrayList<>(); public List<Integer> largestValues(TreeNode root) { if(root==null){ return result; } Queue<TreeNode> queue = new LinkedList<>(); queue.offer(root); int count = 1; while(!queue.isEmpty()){ List<Integer> list = new ArrayList<>(); int floorSize = 0; for(int i=0;i<count;i++){ TreeNode now = queue.poll(); list.add(now.val); if(now.left!=null){ queue.offer(now.left); floorSize++; } if(now.right!=null){ queue.offer(now.right); floorSize++; } } int max = list.get(0); for(Integer x:list){ if(max<x){ max = x; } } count = floorSize; result.add(max); } return result; }}