1. first refused because there are no tables for one (+1)
2. second refused for the same reason (+1)
3. third and four accepted because there is an available table for two (+0).

Finally, there is one empty table for two and another one used for ne group of two clients.

The first and second clients may have been proposed a table for two if a > 0 and if all tables for one were used.

Yes,

1. tables for two can be full moon or last quarter or new moon.
2. tables for one can only be full moon or new moon.

(...looks like moon phases to me... 8o ... XD )

Nice one.
I suggest to add a visual description.

First example :

1 || 🌕 || 🌑 🌑 || 0

2 || 🌕 || 🌕 🌑 || 0

1 || 🌕 || 🌕 🌗 || 0

1 || 🌕 || 🌕 🌕 || 0

Denied : 0

Second example :

1 || 🌕 || 🌑 || 0

1 || 🌕 || 🌗 || 0

2 || 🌕 || 🌗 || 2

1 || 🌕 || 🌕 || 0

Denied : 2

13 people are denied service, and 13 is the expected answer. Where's the problem?

in javascript, total denied number is more than N group, and even bigger than N person, is it a bug?

restaurant( 2, 1, [2,1,2,2,2,2,1,2,1,2] ) = 13 ???