首先明确一个概念
左面内个叫上凸壳,右面那个叫下凸壳
然后我们只需要维护一个上图壳就行了,先按着斜率排序,每次加进来一条边,判断tot边和这个边与tot-1边的交点横坐标,
如果这条边的横坐标小就一直弹栈就好了
/**************************************************************
Problem:
User: BLADEVIL
Language: Pascal
Result: Accepted
Time: ms
Memory: kb
****************************************************************/
//By BLADEVIL
var
n :longint;
a, b, num :array[..] of longint;
quea, queb :array[..] of longint;
tot :longint;
quex :array[..] of double;
ans :array[..] of longint;
i :longint;
procedure swap(var a,b:longint);
var
c :longint;
begin
c:=a; a:=b; b:=c;
end;
procedure qs(low,high:longint);
var
i, j, xx, yy :longint;
begin
i:=low; j:=high; xx:=a[(i+j) div ];
yy:=b[(i+j) div ];
while i<j do
begin
while (a[i]<xx) or (a[i]=xx) and (b[i]>yy) do inc(i);
while (a[j]>xx) or (a[j]=xx) and (b[j]<yy) do dec(j);
if i<=j then
begin
swap(a[i],a[j]);
swap(b[i],b[j]);
swap(num[i],num[j]);
inc(i); dec(j);
end;
end;
if i<high then qs(i,high);
if j>low then qs(low,j);
end;
procedure qs1(low,high:longint);
var
i, j, xx :longint;
begin
i:=low; j:=high; xx:=ans[(i+j) div ];
while i<j do
begin
while ans[i]<xx do inc(i);
while ans[j]>xx do dec(j);
if i<=j then
begin
swap(ans[i],ans[j]);
inc(i); dec(j);
end;
end;
if i<high then qs1(i,high);
if j>low then qs1(low,j);
end;
procedure insert(i:longint);
var
k :longint;
x :double;
begin
if a[i]=quea[tot] then exit;
if tot> then
begin
x:=(queb[tot-]-b[i])/(a[i]-quea[tot-]);
while (tot>) and (x<=quex[tot]) do
begin
dec(tot);
x:=(queb[tot-]-b[i])/(a[i]-quea[tot-]);
end;
end;
inc(tot);
quea[tot]:=a[i];
queb[tot]:=b[i];
quex[tot]:=(queb[tot-]-b[i])/(a[i]-quea[tot-]);
ans[tot]:=num[i];
end;
begin
read(n);
for i:= to n do read(a[i],b[i]);
for i:= to n do num[i]:=i;
qs(,n);
quea[]:=a[]; queb[]:=b[];
quex[]:=-maxlongint; ans[]:=num[];
tot:=;
for i:= to n do insert(i);
qs1(,tot);
for i:= to tot do write(ans[i],' ');
end.