The UMPIRE Method

Edwin Kofler

2022-8-6

As a part of the CTI Accelerate Program, I learned about a problem-solving technique called ‘UMPIRE’. Also used at CodePath, UMPIRE is especially helpful for solving interview questions.

I’m finding the framework especially useful as I haven’t used any problem solving skills in years. It’s time to end my reliance on pattern matching and inertial intuition!

If you’re not familiar with the framework, I’d recommend CodePath’s post about it to get the basics down - this post explains more about how I personally use it, rather than what it is.

In Summary

There are six steps:

1. Understand
2. Match
3. Plan
4. Implement
5. Review
6. Evaluate

I personally broke down this process into 3 larger steps:

1. Understand, Match, and Plan
2. Implement and Review
3. Evaluate

Fewer steps allows me to fit the process into working memory. I’ll name each of the three larger steps comprehension, solution, and application, respectively.

1. Comprehension

Its difficult to write code without understanding the problem. In my view, understanding is the most crucial part. Each subsequent subsection highlights key factors for consideration.

For understanding,

• form of input (type, structure, guarantees, contracts)
• form of output (type, structure, guarantees, contracts)
• convert input to output manually

For matching,

• similar problems
• similar solutions
• identify both similarities and differences

For planning,

• break down problem (identify subcomponents)
• simplify problem (initially assume invariants, but relax them later)
• develop pseudocode

2. Solution

Once the problem space is understood enough, it’s time to build a solution.

For implement and review,

• Correct code (common cases)
• Complete code (corner cases)
• Clean / idiomatic code (less important)
• Debug, debug, debug!

3. Application

Effort exerted in previous steps would be in vain if the solution isn’t used properly. This step helps identify the quality and applicability of the solution.

For evaluate,

• Time complexity
• Space complexity
• Areas for improvement

Wrap

Practically speaking, there’ll be frequent jumping between steps in the problem solving process. But, like most categories, it is important to make a distinction for the sake of improving the process as a whole.

In Practice

To apply this framework, I like to write the initials of each steps in code comments. For example:

# u: input: int, int, int (some items)
# u: output: array<int> (list of things)

# m: linked list, but with ...

# p: for integers 1 and 2 ...
if True:
  pass

# p: for integer 3 ...
if True:
  pass

# e: o(1) time
# e: o(1) space
# e: next time, use std::vector instead of std::list

Wrap

It’s an ongoing process to develop a variant of the UMPIRE method that works for me. When my technique invariably improves, I’ll update this post to match.

I wish to thank the organizers of the CTI program for their effort and dedication towards putting together such an awesome piece of curriculum and community! I encourage you to check them out! 😄