题解 | #二叉树之寻找第k大#

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public 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
     * @param k int整型
     * @return int整型
     */
    public static ArrayList<Integer> arrayList = new ArrayList<>();
    public int kthLargest (TreeNode root, int k) {
        search(root);
        return arrayList.get(arrayList.size() - k);
    }
    public void search(TreeNode root) {
        if (root == null) {
            return;
        }
        search(root.left);
        arrayList.add(root.val);
        search(root.right);
    }
}