SDE - 1

Step 1 : I solved with brute forces using for loop.
Step 2 : The interviewer asked me to optimize the solution.
Step 3 : Then I came up with a log n solution.

A deadlock in OS is a situation in which more than one process is blocked because it is holding a resource and also requires some resource that is acquired by some other process. The four necessary conditions for a deadlock situation to occur are mutual exclusion, hold and wait, no preemption and circular set.

We have a standard approach to system design which is explained more thoroughly in the article here. However, the steps are summarised below:

Requirements clarification: Making sure we have all the information before starting. This may include how many requests or users we are expecting.
Back of the envelope estimation: Doing some quick calculations to gauge the necessary system performance. For example, how much storage or bandwidth do we need?
System interface design: What will our system look like from the outside, how will people interact with it? Generally this is the API contract.
Data model design: What our data will look like when we store it. At this point we could be thinking about relational vs non-relational models.
Logical design: Fitting it together in a rough system! At this point I’m thinking at a level of ‘how would I explain my idea to someone who knows nothing about tech?’
Physical design: Now we start worrying about servers, programming languages and the implementation details. We can superimpose these on top of the logical design.
Identify and resolve bottlenecks: At this stage we will have a working system! We now refine the design.