【BZOJ1208】宠物收养所（splay）

题意：见题面

思路：因为每个时刻要么全是人要么全是宠物，所以可以一棵splay解决

维护单点插入，单点删除，求前驱，求后继即可

var t:array[0..100000,0..1]of longint;
    num,fa:array[0..100000]of longint;
    n,cnt,t1,t2,i,root,p,x,y:longint;
    ans:int64;

procedure rotate(x:longint;var k:longint);
var y,z,l,r:longint;
begin
 y:=fa[x]; z:=fa[y];
 if t[y,0]=x then l:=0
  else l:=1;
 r:=1-l;
 if y=k then k:=x
  else
   if t[z,0]=y then t[z,0]:=x
    else t[z,1]:=x;
 fa[x]:=z; fa[y]:=x; fa[t[x,r]]:=y;
 t[y,l]:=t[x,r]; t[x,r]:=y;
end;

procedure splay(x:longint;var k:longint);
var y,z:longint;
begin
 while x<>k do
 begin
  y:=fa[x]; z:=fa[y];
  if y<>k then
  begin
   if (t[y,0]=x)xor(t[z,0]=y) then rotate(x,k)
    else rotate(y,k);
  end;
  rotate(x,k);
 end;
end;

procedure ins(var k:longint;x,last:longint);
begin
 if k=0 then
 begin
  inc(cnt);
  k:=cnt; num[k]:=x;
  fa[k]:=last; splay(k,root);
  exit;
 end;
 if x<num[k] then ins(t[k,0],x,k)
  else ins(t[k,1],x,k);
end;

procedure del(x:longint);
var k:longint;
begin
 splay(x,root);
 if t[x,0]*t[x,1]=0 then root:=t[x,0]+t[x,1]
  else
  begin
   k:=t[x,1];
   while t[k,0]>0 do k:=t[k,0];
   t[k,0]:=t[x,0]; fa[t[x,0]]:=k;
   root:=t[x,1];
  end;
 fa[root]:=0;
end;

procedure pred(k,x:longint);
begin
 if k=0 then exit;
 if num[k]<=x then
 begin
  t1:=k; pred(t[k,1],x);
 end
  else pred(t[k,0],x);
end;

procedure succ(k,x:longint);
begin
 if k=0 then exit;
 if num[k]>=x then
 begin
  t2:=k; succ(t[k,0],x);
 end
  else succ(t[k,1],x);
end;

begin
 assign(input,'bzoj1208.in'); reset(input);
 assign(output,'bzoj1208.out'); rewrite(output);
 readln(n);
 for i:=1 to n do
 begin
  readln(x,y);
  if root=0 then begin p:=x; ins(root,y,0); end
   else if p=x then ins(root,y,0)
    else
    begin
     t1:=-1; t2:=-1;
     pred(root,y); succ(root,y);
     if t1=-1 then
     begin
      ans:=ans+num[t2]-y; ans:=ans mod 1000000; del(t2);
     end
      else if t2=-1 then
      begin
       ans:=ans+y-num[t1]; ans:=ans mod 1000000; del(t1);
      end
       else
        if y-num[t1]>num[t2]-y then
        begin
         ans:=ans+num[t2]-y; ans:=ans mod 1000000; del(t2);
        end
         else
         begin
          ans:=ans+y-num[t1]; ans:=ans mod 1000000; del(t1);
         end;
    end;
 end;
 writeln(ans);
 close(input);
 close(output);
end.