Stock Price Fluctuation

MediumHeapheap

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Problem

A feed delivers stock price records as (timestamp, price) pairs. Records can arrive out of order, and a later record for a timestamp that was already seen is a **correction** that replaces the earlier price for that timestamp. Implement StockPrice: - StockPrice() starts with no records. - update(timestamp, price) sets the price at timestamp to price (inserting or correcting). - current() returns the price at the **largest** timestamp seen so far. - maximum() returns the highest price among the current (corrected) records. - minimum() returns the lowest price among the current (corrected) records. current, maximum and minimum are only called after at least one update. Aim for O(log n) amortized per operation.

Examples

Input: ["StockPrice","update","update","current","maximum","update","maximum","update","minimum","current"] [[],[1,10],[2,5],[],[],[1,3],[],[4,2],[],[]]
Output: [null,null,null,5,10,null,5,null,2,2]
After the correction at timestamp 1 (10 becomes 3), the prices are {1: 3, 2: 5}, so the maximum drops to 5. Adding {4: 2} makes 2 both the minimum and the latest price.
Input: ["StockPrice","update","update","current","update","minimum","maximum","update","maximum"] [[],[5,8],[3,12],[],[5,1],[],[],[3,1],[]]
Output: [null,null,null,8,null,1,12,null,1]
`current` follows the largest timestamp (5), not the most recent call. Once both timestamps are corrected to 1, the maximum is 1.

Constraints

  • 1 <= timestamp, price <= 10^9
  • At most 10^5 calls are made in total.
  • `current`, `maximum` and `minimum` are called only after at least one `update`.

What the interviewer grades

A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.

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