力扣第 335 场周赛题解

class Solution {

    public int passThePillow(int n, int time) {

        int cur = 1;

        int dir = 1;

        while (--time >= 0) {

            cur += dir;

            if (cur > n) {

                cur = n - 1;

                dir = -1;

            } else if (cur < 1) {

                cur = 2;

                dir = 1;

            } 

        }

        return cur;

    }

}

/**

 * 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 {

    public long kthLargestLevelSum(TreeNode root, int k) {

        List<Long> list = new ArrayList<>();

        Queue<TreeNode> que = new LinkedList<>();

        que.offer(root);

        while (!que.isEmpty()) {

            long sum = 0;

            for (int i = que.size(); i > 0; --i) {

                root = que.poll();

                sum += root.val;

                if (root.left != null) que.offer(root.left);

                if (root.right != null) que.offer(root.right);

            }

            list.add(sum);

        }

        Collections.sort(list);

        return list.size() < k ? -1 : list.get(list.size() - k);

    }

}