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

If you're sorting a sorted list with only a few new out of place trailing items then you should take advantage of the rare case in which insertion sort actually works efficiently. Implementing insertion sort on a sorted list with only a few trailing out of place values can sort in O(n) time. You're just inserting your few out of place values into place, while quick sort is picking a pivot and going through the entire quick sort process. Also, if you're not incorporating some type of efficient pivot selection process into your quick sort, and going with some "average of first 3 items" approach on an already sorted list you're going to be sorting in O(n^2) time.