OJ Board

First of all. Rund DFS from node 0 this will give you all the nodes reachables from 0

then consider n disctinct graph's
let the graph n_i be the same graph g but without the node i

run DFS from 0 in those new graphs

If node J were reachable from 0 in the original graph and were NOT reachable in ...

Just use 2 pointers instead a map.

Suppose we have 2 arrays sorted

a1 a2 ... an-1
b1 b2 ... bm-1

start with ans=0
and
pa=0 and pb=0 the indexes

if( a[pa] == b[pb] ) ans++

then you just advance the pointer in the array which has the least number (if they are equal no matter which you choose ...

AC in 0.9 using scanf/printf and multiset

I got AC in 0.355s Without using shieve.
Fisrt- Found a way of factoring a number, I do the TRIAL DIVISION, (just like factoring by hand) anyway. I think that if you could do it in less time, would be great.
Given the factoring, computing alpha(n) is easy. (I did it in the same function)

Second ...

Yes, you need to round the distance BEFORE sum them. In other words, when you compute the distance between city A and B, store it as the nearest integer. Then apply the algorithm you want- I used C++11 and Floyd I got AC thanks to this forum :)

Also, I applied the formula that comes directly from ...