Having a hash map to keep track of elements in another data structure

Question

So sometimes I have a certain ds with certain functionalities which have a get time complexity of O(N) like a queue, stack, heap, etc.. I use one of these ds in a program which just needs to check whether a certain element is in one of theses ds, but because they have a get complexity of O(N), it is the pitfall in my algorithm.

If memory isn't much of my worries, would it be poor design to have a hashmap which keeps track of the elements in the restricted data structure? Doing this would essentially remove the O(N) restriction and allow it to be O(1).

Answer 1

在许多情况下都有保证补充哈希表。但是，维持“并行哈希”可能会成为一种负担。

当您需要快速检查成员资格时，您描述的情况通常使用基于散列的集合（HashSet<T>，std::unordered_set<T>等建模，具体取决于语言）。这些结构的缺点是没有指定元素的顺序，并且它们不能有重复。

根据库的不同，您可以访问修复这些缺点的数据结构。例如，Java提供了LinkedHashSet<T>，它提供了可预测的枚举顺序，而C ++提供了std::unordered_multiset<T>，它允许重复。