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 int kthLargest (TreeNode root, int k) {
        // write code here
        Queue<Integer> queue = new PriorityQueue<>();
        preOrder(root, queue, k);
        return queue.peek();
    }
    private void preOrder(TreeNode root, Queue<Integer> queue, int k) {
        if (root == null) return;
        queue.offer(root.val);
        if (queue.size() > k) queue.poll();
        preOrder(root.left, queue, k);
        preOrder(root.right, queue, k);
    }
}