set vs unordered_set for fastest iteration

Question

In my application I have the following requirements -

1. The data structure will be populated just once with some values (not key/value pairs). The values may be r

Answer 1

I highly recommend you not to use in such this case. set is binary tree, and unordered_set is hash table - so they use lots of memory, and have slow iteration speed and bad locality of reference. If you have to insert/remove/find data frequently, set or unordered_set good choice, but now you need to just read, store, sort data once and only use data many times.

In this case, sorted vector can be such a good choice. vector is dynamic array, so it has low overhead.

Just directly, see the code.

std::vector data;

int input;
for (int i = 0; i < 10; i++)
{
    std::cin >> input;
    data.push_back(input); // store data
}

std::sort(data.begin(), data.end()); // sort data

That's all. All your data is ready.

If you need to remove duplicates like set, just use unique - erase after sorting.

data.erase(
    std::unique(data.begin(), data.end()),
    data.end()
    );

Notice that you should use lower_bound, upper_bound and equal_range rather than find or find_if to use the benefits of sorted data.