LeetCode--关于在每个树行中找最大值

• 题目描述
• 代码

题目描述

如题

代码

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    private List<Integer> list = new ArrayList<>();
    
    public List<Integer> largestValues(TreeNode root) {
        preOrder(root, 0);
        return list;
    }
    
    private void preOrder(TreeNode root, int level)
    {
        if(root == null)
        {
            return;
        }
        
        if(list.size() == level)
        {
            list.add(root.val);
        }
        else if(root.val > list.get(level))
        {
            list.set(level, root.val);
        }
        
        preOrder(root.left, level + 1);
        preOrder(root.right, level + 1);
    }
}