Simple programming practice (Fizz Buzz, Print Primes)

Question

I want to practice my skills away from a keyboard (i.e. pen and paper) and I'm after simple practice questions like Fizz Buzz, Print the first N primes.

What are your favourite simple programming questions?

Answer 1

Problem: Insert + or - sign anywhere between the digits 123456789 in such a way that the expression evaluates to 100. The condition is that the order of the digits must not be changed.

e.g.: 1 + 2 + 3 - 4 + 5 + 6 + 78 + 9 = 100

Programming Problem: Write a program in your favorite language which outputs all possible solutions of the above problem.

Answer 2

Towers of Hannoi is great for practice on recursion.

I'd also do a search on sample programming interview questions.

Answer 3

There are some good examples of simple-ish programming questions in Steve Yegge's article Five Essential Phone Screen Questions (under Area Number One: Coding). I find these are pretty good for doing on pen and paper. Also, the questions under OOP Design in the same article can be done on pen and paper (or even in your head) and are, I think, good exercises to do.

Answer 4

Quite a few online sites for competitive programming are full of sample questions/challenges, sorted by 'difficulty'. Quite often, the simpler categories in the 'algorithms' questions would suit you I think.

For example, check out TopCoder (algorithms section)!

Apart from that, 2 samples:

1. You are given a list of N points in the plane by their coordinates (x_i, y_i), and a number R>0. Output the maximum number out of the N given points that can be simultaneously covered by a disk of radius R (for bonus points: complexity?).

2. You are given an array of N numbers a1 to aN, and you want to compute a1 * a2 * ... * aN / ai for all values of i (so the output is again an array of N elements) without using division. Provide a (non-naive) method (complexity should be in O(N) multiplications).

Answer 5

I've been working on http://projecteuler.net/

Answer 6

I also like project euler, but I would like to point out that the questions get really tricky really fast. After the first 20 questions or so, they start to be problems most people won't be able to figure out in 1/2 an hour. Another problem is that a lot of them deal with math with really large numbers, that don't fit into standard integer or even long variable types.

Answer 7

If you want a pen and papper kind of exercizes I'd recommend more designing than coding.

Actually coding in paper sucks and it let's you learn almost nothing. Work enviroment does matter so typing in a computer, compiling, seeing what errors you've made, using refactor here and there, just doesn't compare to what you can do on a piece of paper and so, what you can do on a piece of paper, while being an interesting mental exercize is not practical, it will not improve your coding skills so much.

On the other hand you can design the architecture of a medium or even complex application by hand in a paper. In fact I usually do. Engineering tools (such as Enterprise Architect) are not good enough to replace the good all by-hand diagrams.

Good projects could be, How would you design a game engine? Classes, Threads, Storage, Physics, the data structures which will hold everything and so on. How would you start a search engine? How would you design an pattern recognition system?

I find that kind of problems much more rewarding that any paper coding you can do.

Answer 8

Thanks for the answers everyone.

Project Euler was exactly what I was looking for.

To anyone else reading this thread, Steve Yegge's article is also brilliant.