CodingBat
Math and conditionals
- http://codingbat.com/prob/p238805
- http://codingbat.com/prob/p283727
- http://codingbat.com/prob/p283759
- http://codingbat.com/prob/p267977
- http://codingbat.com/prob/p232742
- http://codingbat.com/prob/p208025
Strings
- http://codingbat.com/prob/p253286
- http://codingbat.com/prob/p229309
- http://codingbat.com/prob/p220147
A bit surrpised it seems to simple and yet useful.