Question
Pivot a list of long-format records into a wide table. Each record is a dict with an `index_key`, a `col_key`, and a numeric `val_key`. Produce a 2D table whose first row is a header `['_', col1, col2, ...]` with the distinct column-key values sorted ascending, followed by one row per distinct index value (sorted ascending): `[index_value, v_col1, v_col2, ...]`, using `0` where a given (index, column) pair has no record. Return the table as a list of lists.
pivot(rows: list[dict], index_key: str, col_key: str, val_key: str) → list[list][[{"d":"mon","n":1,"p":"x"},{"d":"mon","n":2,"p":"y"},{"d":"tue","n":3,"p":"x"}],"d","p","n"]out[["_","x","y"],["mon",1,2],["tue",3,0]]State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.