Comparison tricks in C++

Question

A class:

class foo{
public:
    int data;
};

Now I want to add a method to this class, to do some comparison, to see if its data is equal to on

Answer 1

There are many ways of doing this with the STL.

If you have an incredibly large number of items and you want to test if your given item is a member of this set, use set or unordered_set. They allow you to check membership in log n and constant time respectively.

If you keep the elements in a sorted array, then binary_search will also test membership in log n time.

For small arrays, a linear search might however preform significantly faster (as there is no branching). A linear search might even do 3-8 comparisons in the time it takes the binary search to 'jump around'. This blog post suggests there to be a break-even point at proximately 64 items, below which a linear search might be faster, though this obviously depends on the STL implementation, compiler optimizations and your architecture's branch prediction.