leetcode 每日一题 515. 在每个树行中找最大值

leetcode 每日一题 515. 在每个树行中找最大值

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
     private Map<Integer, Integer> map = new TreeMap();

    public List<Integer> largestValues(TreeNode root) {
        dfs(root, 0);
        List<Integer> list = new ArrayList<>();
        list.addAll(map.values());
        return list;
    }

    private void dfs(TreeNode root, Integer i) {
        if (root == null) {
            return;
        }
        if (!map.containsKey(i) || map.get(i) < root.val) {
            map.put(i, root.val);
        }
        dfs(root.left, i + 1);
        dfs(root.right, i + 1);
    }
}