"BZOJ1103" Metropolitan Meg (Dfs sequence, tree array)

Test instructions: There is a tree, 1th points for the root, to ensure that the number of small point depth small, the initial state of each edge is not marked, requires two operations online:

A: Marks the edge of the connection x, Y

W: How many edges are not marked on the path from 1 to X

N<=2*10^5

Idea: The special nature of the subject:

1. Mark only one edge at a time and no heavy edges

2. Direct path of 1 to X without LCA

Record the first and last occurrences of the I point in the DFS sequence B[i] and C[i]

It can be found that if (x, y) (x<y) edge is marked only for the interval (B[y],c[y]) has a 1 contribution

Equivalent to prefix and s[b[y]]++ s[c[y]+1]--

As for s[c[y]+1]--or s[c[y]]--is not important, because the question is definitely s[a[i]], and the DFS sequence will not appear duplicate

Single point modification, tree array prefix and implementation

1 varHead,vet,next,a,b,c,t,flag:Array[1..1000000] ofLongint;2 N,m,tot,i,x,y,time,j,k:longint;3 ch:string;4 5 procedureAdd (a,b:longint);6 begin7 Inc (TOT);8next[tot]:=Head[a];9vet[tot]:=b;Tenhead[a]:=tot; One End; A  - procedureDFS (u:longint); - varE,v:longint; the begin -flag[u]:=1; Inc (time); A[time]:=u; b[u]:=Time ; -e:=Head[u]; -   whileE<>0  Do +  begin -v:=Vet[e]; +   ifflag[v]=0  ThenDfs (v); Ae:=Next[e]; at  End; -Inc (time); A[time]:=u; c[u]:=Time ; - End; -  - functionlowbit (x:longint): Longint; - begin inExit (x and(-x)); - End; to  + functionsum (x:longint): Longint; - begin thesum:=0; *   whileX>0  Do $  beginPanax Notoginsengsum:=sum+T[x]; -x:=x-lowbit (x); the  End; + End; A  the procedureUpdate (x,y:longint); + begin -   whilex<=n<<1  Do $  begin $t[x]:=t[x]+y; -x:=x+lowbit (x); -  End; the End; - Wuyi begin theAssign (input,'bzoj1103.in'); Reset (input); -Assign (output,'Bzoj1103.out'); Rewrite (output); Wu READLN (n); -   fori:=1  toN-1  Do About  begin $ readln (x, y); - Add (x, y); - Add (y,x); -  End; ADfs1); +   fori:=1  toN Do the  begin -Update (B[i],1); $Update (c[i],-1); the  End; the Readln (m); the   fori:=1  ton+m-1  Do the  begin -READLN (CH); x:=0; y:=0; in   ifch[1]='W'  Then the   begin the     forj:=3  toLength (CH) Dox:=x*Ten+ord (Ch[j])-ord ('0'); AboutWriteln (SUM (b[x])-1); the   End; the   ifch[1]='A'  Then the   begin +     forj:=3  toLength (CH) Do -    begin the     ifch[j]=' '  ThenBreak ;Bayix:=x*Ten+ord (Ch[j])-ord ('0'); the    End; thek:=J; -     forj:=k+1  toLength (CH) Doy:=y*Ten+ord (Ch[j])-ord ('0'); -Update (b[y],-1); theUpdate (C[y],1); the   End; the  End; the close (input); - close (output); the End.

"BZOJ1103" Metropolitan Meg (Dfs sequence, tree array)