Question

I am maintaining a fixed-length table of 10 entries. Each item is a structure of like 4 fields. There will be insert, update and delete operations, specified by numeric position. I am wondering which is the best data structure to use to maintain this table of information:

1. array – insert/delete takes linear time due to shifting; update takes constant time; no space is used for pointers; accessing an item using [] is faster.

2. stl vector – insert/delete takes linear time due to shifting; update takes constant time; no space is used for pointers; accessing an item is slower than an array since it is a call to operator[] and a linked list .

3. stl list – insert and delete takes linear time since you need to iterate to a specific position before applying the insert/delete; additional space is needed for pointers; accessing an item is slower than an array since it is a linked list linear traversal.

Right now, my choice is to use an array. Is it justifiable? Or did I miss something?

Which is faster: traversing a list, then inserting a node or shifting items in an array to produce an empty position then inserting the item in that position?

What is the best way to measure this performance? Can I just display the timestamp before and after the operations?

Answer 1

Use STL vector. It provides an equally rich interface as list and removes the pain of managing memory that arrays require.

You will have to try very hard to expose the performance cost of operator[] – it usually gets inlined.

I do not have any number to give you, but I remember reading performance analysis that described how vector<int> was faster than list<int> even for inserts and deletes (under a certain size of course). The truth of the matter is that these processors we use are very fast – and if your vector fits in L2 cache, then it’s going to go really really fast. Lists on the other hand have to manage heap objects that will kill your L2.