Read it Before Code (Algorithm) Interview

Ask how many questions the will ask

Clarify the questions

• Take time to draw some examples to understand the question
  • all different cases, extreme cases
• Ask the range of input
• Duplicate in the data
• Whether I can change/reuse the input
• Ask whether I have used all useful info, whether I missed anything

When Write code

• Extract some functions aggressively
  • Otherwise you may repeat a lot of code
  • Focus the main part first, define what parameters it needs
  • Leave the implementation later, interviewer may just ignore it
• Add To-Check tag where the code may be trick or error prone
  • < or <=, len or len-1;
• What states, variables we need
• How do we change them
• Leave some spaces (where you think you may need add some code later, and if the white board is big)

Recheck the code carefully

• First focus on the main logic, error-prone part
• Also check all code
• Use different (simple) use cases to find the problem in the code/algorithm

Compare different approaches

• Always think whether there are better approaches (and say it)
• The different approaches may be easier to code or have better runtime (or space) complexity
• When you think you can implement it different ways or have different approaches, make sure it works and you choose the one that’s easier to implement
  • Sometimes, the other approach may be not work

Communication

• Le the interviewer your thinking process, different approaches you are trying

What data structures to use:

• Stack
• PriorityQueue
  • Examples: LeetCode 767 - Reorganize String

  MultiChar mc1 = pq.poll(), mc2 = pq.poll();
  if (--mc1.count > 0) pq.add(mc1);
  if (--mc2.count > 0) pq.add(mc2);
  

• TreeMap, TreeSet\
  • Use it when need keep some order
  • Need (binary) search the key
  • Examples: Interval

Interval

• TreeMap, sort by start or end