Clarify the problem and edge cases, then propose a monotonic stack solution that processes the array from right to left to find the nearest smaller element to the right. Explain how the stack maintains indices of potential candidates, and analyze time and space complexity as O(n).
Pro tip: Emphasize that the monotonic stack works because we only need the nearest smaller element to the right, and any elements that are larger than the current can be discarded as they will never be the answer for earlier elements. This demonstrates deep understanding of the technique.
Restate the problem in your own words, confirm that tasks execute right to left, and discuss edge cases like empty array, single element, all increasing/decreasing, and duplicates.
Mention that a naive O(n^2) solution would check each element against all elements to its right, but this is inefficient for large inputs.
Explain that you will traverse the array from right to left, maintaining a stack of indices with strictly increasing priorities from top to bottom (or decreasing, depending on implementation). For each element, pop elements from the stack that are greater than or equal to the current priority, then the top of the stack (if any) is the nearest smaller element to the right.
Trace the algorithm on a small example, showing how the stack evolves and how duplicates are handled (e.g., by popping equal elements to ensure strict inequality).
State that each element is pushed and popped at most once, giving O(n) time and O(n) space. Mention that this handles large inputs efficiently and is suitable for Amazon's scale.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.