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Solution: Next Greater Element IV

Explore how to solve the second greater element problem using stacks. This lesson guides you through maintaining two stacks to track elements awaiting their first and second greater values, enabling a linear time and space complexity solution. By understanding this method, you will efficiently implement the approach in C++ and improve problem-solving skills for coding interviews.

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:

  • ...