The Design Patterns That Come Up in This Round

A design pattern is a named solution to a problem that keeps happening. There are dozens of them. Six appear in this round often enough to be worth knowing by name.

Knowing the name is worth something. It turns a paragraph of explanation into two words. It also tells the interviewer you have seen the problem before.

Using a pattern where it does not belong costs more than not knowing it. So each pattern below comes with the signal that says it applies.

Strategy

The signal: one operation has several interchangeable versions, and the right one is chosen at run time.