Erlang Interview Questions and Answers

1-5 — Project Euler
6 — XML over REST sample
7 — Massive Spawn
8 — GTIN validator
SQL — sample SQL

Compile

$ git clone http://github.com/5HT/interview && cd interview
$ ./mad dep com pla rep

Test

1. Dividers Below 1000

> i:dividers35().
233168

2. Prime Factors of 600851475143

> i:pfactors().
233168

3. Even Fib Sum Below 4000000

> i:fibs().
4613732

4. Palindroms from 101 to 999

> i:palindroms().
906609

5. Dividers Below 20

> i:solve().
232792560

6. XML over REST sample

$ curl -X POST -H 'Content-type: text/xml' -d @priv/Test.xml http://localhost:8080/capture
$ cat priv/test.csv

7. Massive Spawn

While running test on 1M numbers a bit timeless, you can observe current calculations as follow:

> gen_server:call(i:cache(api),{info}).
{state,api,1001455,524,1000456}
17> length(supervisor:which_children(i)).
999
18> supervisor:which_children(i).
[{{worker,233690},<0.22658.21>,worker,[i_node]},
 {{worker,233689},<0.22655.21>,worker,[i_node]},
 {{worker,233688},<0.22652.21>,worker,[i_node]},
 {{worker,233666},<0.22583.21>,worker,[...]},
 {{worker,233665},<0.22580.21>,worker,...},
 {{worker,...},<0.22577.21>,...},
 {{...},...},
 {...}|...]

Current max length of sequence 524 of first 1000456 natural numbers. Note that CPU avg is about 70% with a pool of 1000 processes.

8. GTIN validator

> i:validate({gtin,"04250021234506"}).
ok
7> i:validate({gtin,"04250021234502"}).
{error,{checksum,4}}

9. SQL sample

initdb -D /usr/local/var/postgres
createdb `whoami`
psql -d `whoami` -f init.sql

marikutsa / interview