Excel validation lists avoid blanks and errors with TOCOL(ignore) plus FILTER; the spill range stays stable across worksheets.

Exploring data, one index at a time.

The "Sort an Array" problem contains biased test cases that cause mathematically correct and efficient QuickSort implementations to receive Time Limit Exceeded (TLE) errors, while the built-in ...

If you want to solve a tricky problem, it often helps to get organized. You might, for example, break the problem into pieces and tackle the easiest pieces first. But this kind of sorting has a cost.

Have you ever struggled to sort data in Excel in a way that truly fits your needs? Imagine trying to organize a list of regions not alphabetically, but in a specific order like “North, South, East, ...