SPSEQ - Sequences

Tác giả: flashmt

Ngôn ngữ: Pascal

const fi='';
      fo='';
      maxn=100001;
type ar=array[0..maxn] of longint;
var n,re,num,max:longint;
    a,d,e,f,inc,dec:ar;

procedure rf;
var i:longint;
begin
     assign(input,fi); reset(input);
     read(n);
     for i:=1 to n do
     begin
          read(a[i]);
          d[i]:=i;
     end;
     close(input);
end;

procedure sort(l,r:longint);
var i,j,x,y:longint;
begin
     i:=l; j:=r; x:=a[(i+j) shr 1];
     repeat
           while a[i]<x do i:=i+1;
           while a[j]>x do j:=j-1;
           if i<=j then
           begin
                y:=a[i]; a[i]:=a[j]; a[j]:=y;
                y:=d[i]; d[i]:=d[j]; d[j]:=y;
                i:=i+1; j:=j-1;
           end;
     until i>j;
     if i<r then sort(i,r);
     if l<j then sort(l,j);
end;

procedure edit;
var i:longint;
begin
     a[0]:=-1;
     for i:=1 to n do
     begin
          e[d[i]]:=i;
          if a[i]=a[i-1] then d[i]:=d[i-1]
          else d[i]:=d[i-1]+1;
     end;
     max:=d[n];
end;

function getmax(x,y:longint):longint;
begin
     if x>y then getmax:=x else getmax:=y;
end;

procedure add(x,t:longint);
begin
     while x<=max do
     begin
          if f[x]<t then f[x]:=t else exit;
          x:=x+x and (-x);
     end;
end;

function calc(x:longint):longint;
var r:longint;
begin
     r:=0;
     while x>0 do
     begin
          r:=getmax(r,f[x]);
          x:=x-x and (-x);
     end;
     calc:=r;
end;

procedure pr;
var i,x,t:longint;
begin
     sort(1,n);
     edit;
     for i:=1 to n do
     begin
          x:=d[e[i]];
          t:=calc(x-1);
          inc[i]:=t+1;
          add(x,t+1);
     end;
     fillchar(f,sizeof(f),0);
     for i:=n downto 1 do
     begin
          x:=d[e[i]];
          t:=calc(x-1);
          dec[i]:=t+1;
          add(x,t+1);
     end;
     re:=0;
     for i:=1 to n do
     begin
          if inc[i]<dec[i] then t:=inc[i] shl 1-1
          else t:=dec[i] shl 1-1;
          if t>re then re:=t;
     end;
end;

procedure wf;
begin
     assign(output,fo); rewrite(output);
     writeln(re);
     close(output);
end;

begin
     rf;
     pr;
     wf;
end.

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