C++ - Fastest way to add an item to a sorted array

Question

I\'ve got a database with approximately 200 000 items, which is sorted by username. Now when I add an item to end of array and call my quick sort function to sort that array it

Answer 1

Reinventing the wheel is fine if you want to learn how to code binary search, otherwise reusing is better.

std::lower_bound performs a binary search on a sorted range [first, last), returning an iterator to the searched element x if already present; otherwise the iterator would be pointing to the first element greater than x. Since standard containers' exposing an insert would insert before the iterator, this iterator can be used as-is. Here's a simple example.

#include 
#include 
#include 
#include 

int main()
{
    std::list data = { 1, 5, 7, 8, 12, 34, 52 };

    auto loc = std::lower_bound(data.begin(), data.end(), 10);
    // you may insert 10 here using loc
    std::cout << *loc << '\n';

    loc = std::lower_bound(data.begin(), data.end(), 12);
    // you may skip inserting 12 since it is in the list (OR)
    // insert it if you need to; it'd go before the current 12
    std::cout << *loc << '\n';
}

12

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