"CF700B" Connecting universities (idea problem, greed, shortest path on tree)

Test instructions: Give the 2*K nodes on a tree, pair them up, make them the distance between them and maximum.

Idea: The sides of a side if there is no given node on one side will not be passed ...

If there are 1 nodes will be passed 1 times ...

If there are x, Y nodes on each side, they will be passed min (x, y) times

Because the biggest way is to make each road walk the most times

Must be on each side to take one of the rest can only be solved in one side

So click here to Count

That's a big answer, INT64.

1 varHead,vet,next,a,b,c,dep,flag,f:Array[1..500000] ofLongint;2 N,k,tot,i:longint;3 Ans:int64;4 5 procedureAdd (a,b:longint);6 begin7 Inc (TOT);8next[tot]:=Head[a];9vet[tot]:=b;Tenhead[a]:=tot; One End; A  - functionmin (x,y:longint): Longint; - begin the  ifX<y Thenexit (x); - exit (y); - End; -  + procedureDFS (u,fa:longint); - varE,v:longint; + begin Aflag[u]:=1; ate:=Head[u]; -   whileE<>0  Do -  begin -v:=Vet[e]; -   if(V&LT;&GT;FA) and(flag[v]=0) Then -   begin indep[v]:=dep[u]+1; - DFS (v,u); tof[u]:=f[u]+F[v]; +   End; -e:=Next[e]; the  End; * End; $ Panax Notoginseng begin - read (n,k); the   fori:=1  to 2*k Do +  begin A read (c[i]); thef[c[i]]:=1; +  End; -   fori:=1  toN-1  Do $  begin $ read (a[i],b[i]); - Add (A[i],b[i]); - Add (B[i],a[i]); the  End; -Dfs1,-1);Wuyi   fori:=1  toN-1  Do the   ifDep[a[i]]>dep[b[i]] ThenAns:=ans+min (F[a[i]),2*k-F[a[i]]) -    ElseAns:=ans+min (F[b[i]),2*k-F[b[i]]); Wu writeln (ans); -  About End.

"CF700B" Connecting universities (idea problem, greed, shortest path on tree)