HKI Mock NOI 2015 problem — Graph ? Dynamic Connectivity ?

#	User	Rating
1	ecnerwala	3648
2	Benq	3580
3	orzdevinwang	3570
4	cnnfls_csy	3569
5	Geothermal	3568
6	tourist	3565
7	maroonrk	3530
8	Radewoosh	3520
9	Um_nik	3481
10	jiangly	3467

#	User	Contrib.
1	maomao90	174
2	awoo	164
2	adamant	164
4	TheScrasse	159
4	nor	159
6	maroonrk	156
7	-is-this-fft-	150
8	SecondThread	147
9	orz	146
10	pajenegod	145

Hello everyone !

I've just seen this 2 problem : B/Travel & C/Lilypads in HKI Mock NOI 2015 (seems like it's a Mock contest of Singaporean coders) but I couldn't find out any fast enough solutions for them.

Here are the links to the problems :

B : https://dunjudge.me/analysis/problems/697/

C : https://dunjudge.me/analysis/problems/694/

In problem B, I tried to implement a lot of solutions (e.g. remove each edge and find the shortest path between two vertices that it connects, ...) but that is just enough to pass the first 4 subtasks (which helps me gain <= 50% of the points).

In problem C, I think it's a kind of Dynamic Connectivity problem. I've heard about some data structures that can solve this problem. If my memory is correct, link-cut tree can solve it but many people say that it's really hard to code it in a contest.

Now I'm really stuck and trying to find a help which could leads me to a bright future. Can you please tell me how can I solve these problems. Thank you !