Читать книгу Algorithms For Dummies - John Paul Mueller, John Mueller Paul, Luca Massaron - Страница 35

A brute-force solution is one in which you try each possible answer, one at a time, to locate the best possible answer. (This is also called an exhaustive approach, mostly because you’re so tired when you finish.) It’s thorough, this much is certain, but it also wastes time and resources in most cases. Testing every answer, even when it’s easy to prove that a particular answer has no chance of success, wastes time that an algorithm can use on answers that have a better chance of success. In addition, testing the various answers using this approach generally wastes resources, such as memory. Think of it this way: You want to break the combination for a lock, so you begin at 0, 0, 0, even though you know that this particular combination has no chance of success given the physical characteristics of combination locks. A brute-force solution would proceed with testing 0, 0, 0 anyway and then move on to the equally ridiculous 0, 0, 1.

Every solution type does come with advantages, although sometimes quite small. A brute-force solution has one such advantage. Because you test every answer, you don’t need to perform any sort of preprocessing. The time saved in skipping the preprocessing, though, is unlikely to ever pay back the time lost in trying every answer. However, you may find occasion to use a brute-force solution when

 Finding a perfect solution, if one exists, is essential.

 The problem size is limited.

 You can use heuristics to reduce the size of the solution set.

 Simplicity of implementation is more important than speed.