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Solution: Next Greater Element IV

Understand how to implement a stack-based algorithm that determines the second greater element for each number in an array. This lesson guides you through managing two stacks to track first and second greater elements, enabling a single-pass linear time solution. You'll gain skills to apply stack concepts efficiently to similar coding interview problems.

Statement

You are given a 0-indexed array of non-negative integers nums. For each element nums[i], determine its second greater element and return an array res where res[i] contains the second greater element of nums[i].

The second greater element of nums[i] is defined as the value nums[j] such that:

  • j > i

  • nums[j] > nums[i]

  • There exists exactly one index k where i < k < j and nums[k] > nums[i]

If no such index j exists, then the second greater element for nums[i] is -1.

Constraints:

  • ...