CODEWITHSUNDEEP
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Dmitry Bubnenkov
Dmitry Bubnenkov

Reputation: 9859

How to check if any element of array in another array?

I have got string aabbccddffgg I need to check if it have at last one element from array: ["bb", "cc"].

What is the best way to do it in D?

Upvotes: 3

Views: 92

Answers (1)

greenify
greenify

Reputation: 1127

find and canFind support a variadic number of needles, so using them is the easiest:

"aabbccddffgg".canFind("bb", "cc");

Learn more about std.algorithm.searching.canFind here. If you don't know the number of needles at compile-time, it depends a bit on how much you know about the string, but the naive approach would be to loop multiple times over the string:

auto eles = ["bb", "cc"];
eles.any!(e => "aabbccddffgg".canFind(e)))

If you know more about the sub elements, there are better approaches. For example, if you know that all needles have all the length n, you could create a sliding window of size n and check whether your needles occur in one of the sliding windows:

auto eles = ["bb", "cc"];
"aabbccddffgg".slide(2).canFind!(e => eles.canFind!equal(e));

Learn more about std.range.slide here. The same idea also works in the general case:

auto eles = ["bb", "cc"];
string s = "aabbccddffgg";
s.enumerate
   .map!(e => s.drop(e.index))
   .canFind!(e => eles.canFind!(reverseArgs!startsWith)(e));

Note that drop uses slicing and happens lazily in O(1) without any memory allocation.

Of course, there are still more efficient approaches with more advanced string matching algorithms.

Upvotes: 5

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