Look for these signs that Aliens Trick applies:
"Exactly " constraint in the problem statement (not "at most ").
Standard DP would require with large dimension, making it too slow.
It's a partition, grouping, or selection problem where you're choosing how to divide things.
Convex cost structure: adding one more item/segment gives diminishing returns. If you see all four patterns, try the Aliens Trick. It's rare but transforms problems from to , making otherwise impossible problems solvable.