PBCSEQ - Các đoạn nguyên
Tác giả: RR
Ngôn ngữ: Pascal
{$R+,Q+}
program PBCSEQ;
const
FINP='';
FOUT='';
MAXN=100000;
oo=1000000;
var
kq,n:longint;
a,b:array[1..MAXN] of longint;
d:array[1..oo] of longint;
function max(a,b:longint):longint;
begin
if a>b then max:=a else max:=b;
end;
procedure inp;
var
f:text;
i:longint;
begin
assign(f,FINP); reset(f);
readln(f,n);
for i:=1 to n do
readln(f,a[i],b[i]);
close(f);
end;
procedure swap(var a,b:longint);
var
temp:longint;
begin
temp:=a; a:=b; b:=temp;
end;
procedure sort(l,r:longint);
var
mida,midb,i,j:longint;
begin
i:=l; j:=r; mida:=a[(l+r) div 2]; midb:=b[(l+r) div 2];
repeat
while (a[i]>mida) or ((a[i]=mida) and (b[i]<midb)) do inc(i);
while (a[j]<mida) or ((a[j]=mida) and (b[j]>midb)) do dec(j);
if i<=j then
begin
swap(a[i],a[j]);
swap(b[i],b[j]);
inc(i); dec(j);
end;
until i>j;
if i<r then sort(i,r);
if l<j then sort(l,j);
end;
procedure ans;
var
f:text;
begin
assign(f,FOUT); rewrite(f);
writeln(f,kq);
close(f);
end;
function get(u:longint):longint;
var
kq,v:longint;
begin
kq:=d[u];
v:=u-u and (u xor (u-1));
if v>0 then kq:=max(kq,get(v));
get:=kq;
end;
procedure update(u,k:longint);
var
v:longint;
begin
d[u]:=max(d[u],k);
v:=u+u and (u xor (u-1));
if v<=oo then update(v,k);
end;
procedure solve;
var
i,u:longint;
begin
kq:=0;
for i:=1 to n do
begin
u:=get(b[i]);
if u+1>kq then kq:=u+1;
update(b[i],u+1);
end;
end;
begin
inp;
sort(1,n);
solve;
ans;
end.