1. is it possible that there was no solution at all ?

2. number of various dishes , means total number of dishes or total number of kinds of the dishs?

thanks.

1).No
because
2).You've got unlimited reserve of dishes. We've got a total number of kinds of dishes.
3). Whats up with Test 13???Last solvings got WA and TL...

my reason for not passing Test 13 was using one dimensional table in DP instead of two dimensional. Can some one make up a test that makes one dimensional DP fail?

Try this

3 4
a 2 2
b 1 1
c 1 1

Good one! :)