When Bitmask DP?

Use bitmask DP (dynamic programming) when:

$1.$ You need to track which elements from a small set ($n \leq 20$) have been used.

$2.$ The problem involves permutations, matchings, or visiting all items.

$3.$ Brute force is $O(n!)$ but $O(2^n)$ is acceptable. Signals: "visit all cities exactly once", "assign workers to tasks", "partition into subsets". If $n > 20$, $2^n$ is too large. $2^{20} \approx 1$ million is fine. $2^{25} \approx 33$ million is borderline.