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Solution: Next Greater Element IV

Explore how to efficiently find the second greater element for each item in a numeric array by using two stacks to track first and second greater elements. This lesson helps you understand the algorithm's mechanics, achieve O(n) time complexity, and implement the solution confidently.

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:

  • ...