list

How to initialize List object in Java?

If you check the API for List you’ll notice it says: Being an interface means it cannot be instantiated (no new List() is possible). If you check that link, you’ll find some classes that implement List: All Known Implementing Classes: AbstractList, AbstractSequentialList, ArrayList, AttributeList, CopyOnWriteArrayList, LinkedList, RoleList, RoleUnresolvedList, Stack, Vector Some of those can be instantiated (the ones that are not defined as abstract class). Use their links to know more about them, I.E: to … Read more

IndexError: list index out of range and python

If you have a list with 53 items, the last one is thelist[52] because indexing starts at 0. From Real Python: Understanding the Python Traceback – IndexError: IndexError The IndexError is raised when you attempt to retrieve an index from a sequence, like a list or a tuple, and the index isn’t found in the sequence. The Python documentation defines when this exception is … Read more

How do I find the duplicates in a list and create another list with them?

To remove duplicates use set(a). To print duplicates, something like: Note that Counter is not particularly efficient (timings) and probably overkill here. set will perform better. This code computes a list of unique elements in the source order: or, more concisely: I don’t recommend the latter style, because it is not obvious what not seen.add(x) is doing (the set add() method always returns None, hence … Read more

Check if two unordered lists are equal

Python has a built-in datatype for an unordered collection of (hashable) things, called a set. If you convert both lists to sets, the comparison will be unordered. Documentation on set EDIT: @mdwhatcott points out that you want to check for duplicates. set ignores these, so you need a similar data structure that also keeps track of the number of … Read more

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