#2454

Next Greater Element IV

hard · verified · 41.5% accepted · 749 likes · top 22%

array · binary search · stack · sorting · heap (priority queue) · monotonic stack

Description

You are given a 0-indexed array of non-negative integers nums. For each integer in nums, you must find its respective second greater integer.

The second greater integer of nums[i] is nums[j] such that:

- j > i

- nums[j] > nums[i]

- There exists exactly one index k such that nums[k] > nums[i] and i < k < j.

If there is no such nums[j], the second greater integer is considered to be -1.

- For example, in the array [1, 2, 4, 3], the second greater integer of 1 is 4, 2 is 3, and that of 3 and 4 is -1.

Return an integer array answer, where answer[i] is the second greater integer of nums[i].

Example 1:

Input: nums = [2,4,0,9,6]

Output: [9,6,6,-1,-1]

Explanation:

0th index: 4 is the first integer greater than 2, and 9 is the second integer greater than 2, to the right of 2.

1st index: 9 is the first, and 6 is the second integer greater than 4, to the right of 4.

2nd index: 9 is the first, and 6 is the second integer greater than 0, to the right of 0.

3rd index: There is no integer greater than 9 to its right, so the second greater integer is considered to be -1.

4th index: There is no integer greater than 6 to its right, so the second greater integer is considered to be -1.

Thus, we return [9,6,6,-1,-1].

Example 2:

Input: nums = [3,3]

Output: [-1,-1]

Explanation:

We return [-1,-1] since neither integer has any integer greater than it.

Solution