I think the answer:
0 1 3 4 6 7

1 2 3 4 6 7

How can you measure 1???

I think: 0 2 3 4 6 7

How can you measure 2???
When you fill the third can, and put 3 to the second one, then the second can has 3,and the third one has 1.

It is simple. just fill the second, pour it in the third. Then fill the second again and pour 1 L to the third. Finally there are 2 L in the second.

ok, you're right.

so the answer is:
1 2 3 4 6 7

yes, but i still can't understand how to make it in C++. :(((((

the solution is:1 2 3 4 6 7
why 5 isn't an answer?
while the second has 2,pour it to the third,and fill the second again.

While the second has 2, the third is already filled completely. So you can not pour second to the third...