The ocean is to the right of the buildings. A building has an ocean view if the building can see the ocean without obstructions. Formally, a building has an ocean view if all the buildings to its right have a smaller height.
Return a list of indices (0-indexed) of buildings that have an ocean view, sorted in increasing order.
Example 1:
Input: heights = [4,2,3,1]
Output: [0,2,3]
Explanation: Building 1 (0-indexed) does not have an ocean view because building 2 is taller.
Example 2:
Input: heights = [4,3,2,1]
Output: [0,1,2,3]
Explanation: All the buildings have an ocean view.
Example 3:
Input: heights = [1,3,2,4]
Output: [3]
Explanation: Only building 3 has an ocean view.
You are given an array nums consisting of positive integers.
You can perform the following operation on the array any number of times:
- Choose any two adjacent elements and replace them with their sum.
For example, if nums = [1,2,3,1], you can apply one operation to make it [1,5,1].
Return the minimum number of operations needed to turn the array into a palindrome.
Example 1:
Input: nums = [4,3,2,1,2,3,1]
Output: 2
Explanation: We can turn the array into a palindrome in 2 operations as follows:
- Apply the operation on the fourth and fifth element of the array, nums becomes equal to
[4,3,2,3,3,1]. - Apply the operation on the fifth and sixth element of the array, nums becomes equal to
[4,3,2,3,4].
The array [4,3,2,3,4] is a palindrome. It can be shown that 2 is the minimum number of operations needed.
Example 2:
Input: nums = [1,2,3,4]
Output: 3
Explanation: We do the operation 3 times in any position; at the end, we obtain the array [10], which is a palindrome.
这组 TikTok 面试题考察的是经典的数组扫描与双指针 / 贪心思维。第一题“海景楼”可以从右向左遍历，维护右侧最高楼层，只有当前高度严格大于历史最高值时才拥有海景，最后再按下标升序返回即可，时间复杂度 O(n)。第二题“最少合并成回文”由于每次只能合并相邻元素且所有数为正，可以用左右双指针从两端向中间收缩：如果左右和相等就同时移动，不等时总是合并较小的一侧来拉近两边和，统计合并次数即可得到最小操作数，整体也是 O(n) 且不需要额外复杂数据结构。
