Find the computational complexity of a concatenated system I have a network which includes $L$ blocks ($B_1,\cdots,B_L$) connected one after the other. I have an algorithm having computational complexity $\mathcal{O}(N)$ which runs in each block individually.  

I first run the algorithm  on $B_1$ and get the output. Based on that output, I select the second data set in $B_2$. Then run the same algorithm on $B_2$ and get the output, and so on till $B_L$. The important thing is that the present data set depends on the previous block output. 

Now I want to know the overall system complexity. I guess it is  $\mathcal{O}(LN)$. Is that right?
To summarize what you're saying:


You have an algorithm that runs in $O(n)$.
You're running it on $L$ different blocks, sequentially (no parallelism).
Every block has size $N$.


In this case, the total running time is indeed $O(LN)$.