Finding the pair matched to given sum

Hi guys .
I'm struggling to implement in C a function that gets as two inputs , one input is an integer array, second input is the given sum.
the function returns the pairs of two element that its sum equal to the given sum.
I don't have much experience in C , and I started to implement the function by myself.


I've seen the solution here step by step :
Most commonly asked programming interview question and Answer #GOOGLE - YouTube
but I really didn't understand the logic of the explained code in the video, could anyone please explain to me the algorithm / the code that's explained on the video?
how really we find the matched two pairs that its sum equal to the given sum?


For me a pseudo code is also awesome to understand the solution of the problem.


Much appreciated.

So are you here to get help with your programming assignment, or to spam 30 minute trash youtube videos?

> I don't have much experience in C
Compared to your other recent assignments, this seems quite easy.
If you mooch off the good will of other people for too long, your programming career will be short. You NEED to do the work yourself, not just watch other people do it.

> and I started to implement the function by myself.
So post your best effort so far.

I guess we all know who you are and what you are now 'RyanC'
challenged problem C++ implementation - homework help (preparing for an interview).