bzoj1036

树链剖分的基本题
详细介绍在http://blog.sina.com.cn/s/blog_7a1746820100wp67.html
通过树链剖分我们就可以在树上做线段树操作，完成解答

 const inf=;
 type node=record
        po,next:longint;
      end;
      point=record
        max,sum:longint;
      end;

 var tree:array[..] of point;
     size,d,fa,p,b,c,top:array[..] of longint;
     w:array[..] of node;
     len,i,n,m,x,y,t:longint;
     ch:char;
     s:string;

 function max(a,b:longint):longint;
   begin
     if a>b then exit(a) else exit(b);
   end;

 procedure update(i:longint);
   begin
     tree[i].sum:=tree[i*].sum+tree[i*+].sum;
     tree[i].max:=max(tree[i*].max,tree[i*+].max);
   end;

 procedure swap(var a,b:longint);
   var c:longint;
   begin
     c:=a;
     a:=b;
     b:=c;
   end;

 procedure add(x,y:longint);
   begin
     inc(len);
     w[len].po:=y;
     w[len].next:=p[x];
     p[x]:=len;
   end;

 procedure dfs1(x:longint);  //预处理
   var i,y:longint;
   begin
     i:=p[x];
     size[x]:=;
     while i<> do
     begin
       y:=w[i].po;
       if fa[x]<>y then
       begin
         fa[y]:=x;
         d[y]:=d[x]+;
         dfs1(y);
         size[x]:=size[x]+size[y];
       end;
       i:=w[i].next;
     end;
   end;

 procedure dfs2(x:longint);
   var i,y,q:longint;
   begin
     i:=p[x];
     inc(t);
     c[x]:=t;
     q:=;
     while i<> do
     begin
       y:=w[i].po;
       if (c[y]=) and (size[q]<size[y]) then q:=y;
       i:=w[i].next;
     end;
     if q<> then
     begin
       top[q]:=top[x];  //重儿子先访问
       dfs2(q);
     end;
     i:=p[x];  //然后访问轻儿子
     while i<> do
     begin
       y:=w[i].po;
       if c[y]= then
       begin
         top[y]:=y;
         dfs2(y);
       end;
       i:=w[i].next;
     end;
   end;

 procedure build(i,l,r:longint);
   var m:longint;
   begin
     if l=r then
     begin
       tree[i].sum:=b[l];
       tree[i].max:=b[l];
     end
     else begin
       m:=(l+r) shr ;
       build(i*,l,m);
       build(i*+,m+,r);
       update(i);
     end;
   end;

 procedure add(i,l,r:longint);
   var m:longint;
   begin
     if l=r then
     begin
       tree[i].sum:=y;
       tree[i].max:=y;
     end
     else begin
       m:=(l+r) shr ;
       if x<=m then add(i*,l,m) else add(i*+,m+,r);
       update(i);
     end;
   end;

 function getmax(i,l,r,x,y:longint):longint;
   var m,t:longint;
   begin
     if (x<=l) and (y>=r) then exit(tree[i].max)
     else begin
       m:=(l+r) shr ;
       t:=-inf;
       if x<=m then t:=max(t,getmax(i*,l,m,x,y));
       if y>m then t:=max(t,getmax(i*+,m+,r,x,y));
       exit(t);
     end;
   end;

 function getsum(i,l,r,x,y:longint):longint;
   var m,t:longint;
   begin
     if (x<=l) and (y>=r) then exit(tree[i].sum)
     else begin
       m:=(l+r) shr ;
       t:=;
       if x<=m then t:=t+getsum(i*,l,m,x,y);
       if y>m then t:=t+getsum(i*+,m+,r,x,y);
       exit(t);
     end;
   end;

 function asksum(x,y:longint):longint;
   var f1,f2:longint;
   begin
     asksum:=;
     f1:=top[x];
     f2:=top[y];
     while f1<>f2 do
     begin
       if d[f1]>=d[f2] then
       begin
         asksum:=asksum+getsum(,,n,c[f1],c[x]);
         x:=fa[f1];
       end
       else begin
         asksum:=asksum+getsum(,,n,c[f2],c[y]);
         y:=fa[f2];
       end;
       f1:=top[x];
       f2:=top[y];
     end;
     if c[x]>c[y] then swap(x,y);
     asksum:=asksum+getsum(,,n,c[x],c[y]);
   end;

 function askmax(x,y:longint):longint;
   var f1,f2,t:longint;
   begin
     t:=-inf;
     f1:=top[x];
     f2:=top[y];
     while f1<>f2 do  //提取
     begin
       if d[f1]>=d[f2] then
       begin
         t:=max(t,getmax(,,n,c[f1],c[x]));
         x:=fa[f1];
       end
       else begin
         t:=max(t,getmax(,,n,c[f2],c[y]));
         y:=fa[f2];
       end;
       f1:=top[x];
       f2:=top[y];
     end;
     if c[x]>c[y] then swap(x,y);
     t:=max(t,getmax(,,n,c[x],c[y]));
     exit(t);
   end;

 begin
   readln(n);
   for i:= to n- do
   begin
     readln(x,y);
     add(x,y);
     add(y,x);
   end;
   d[]:=;
   dfs1();
   t:=;
   top[]:=;
   dfs2();
   for i:= to n do
     read(b[c[i]]);
   build(,,n);
   readln(m);
   for i:= to m do
   begin
     read(ch);
     s:='';
     while ch<>' ' do
     begin
       s:=s+ch;
       read(ch);
     end;
     readln(x,y);
     if s='QMAX' then
       writeln(askmax(x,y))
     else if s='QSUM' then
       writeln(asksum(x,y))
     else if s='CHANGE' then
     begin
       x:=c[x];
       b[x]:=y;
       add(,,n);
     end;
   end;
 end.