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Solution: Next Greater Element IV

Understand how to identify the second greater element for each element in an array by using two stacks to track elements waiting for first and second greater values. This lesson teaches you an efficient O(n) time and space complexity method, leveraging stack operations for coding interview problem-solving.

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:

  • ...