I get a Wrong answer on test case 6 on this problem. Would it be possible (and legal, of course) for me to see the test case and/or a similar case that demonstrates why my solution is incorrect so I can test it locally?

I need a hint ( or test case ) aswell. I was looking for an TLE error but instead I got WA.

This test helped me to resolve WA6:
4 4
1 2 2
2 3 2
3 4 2
4 2 2

Answer is:
1.00
1.00
1.00
1.00