Window function running sum
Your task
Implement a SQL window function: SUM(amount) OVER (PARTITION BY account ORDER BY ts). Given rows as [account, ts, amount] (ts integers, may arrive out of order), return for each input row, in the ORIGINAL input order, a [account, ts, running_sum] triple where running_sum is the cumulative amount for that account up to and including that row's ts (rows with equal ts within an account are all included). Assume (account, ts) is unique. Up to 5000 rows.
Examples
running_sum_window(rows: list[list]) -> list[list]Example 1
Input
running_sum_window([["a", 1, 10], ["a", 2, 5], ["a", 3, 20]])Output
[["a", 1, 10], ["a", 2, 15], ["a", 3, 35]]