【BZOJ1031】字符加密Cipher（后缀数组）

题意：将一个长度为2n（复制粘贴后）的字符串的所有长度为n的后缀从小到大排序，并依次输出它们的最后一个字母。

n<=100000

思路：裸SA，模板真难背

P党不得不写成C++风格

var ch:array[0..300000]of char;
    a,x,y,wc,wd,sa:array[0..300000]of longint;
    n,i,m:longint;
    tmp:char;
 
function cmp(a,b,l:longint):boolean;
begin
 exit((y[a]=y[b])and(y[a+l]=y[b+l]));
end;
 
procedure swap(var x,y:longint);
var t:longint;
begin
 t:=x; x:=y; y:=t;
end;
 
procedure getsa;
var i,j,p:longint;
begin
 for i:=0 to n-1 do
 begin
  x[i]:=a[i];
  inc(wc[a[i]]);
 end;
 for i:=1 to m do wc[i]:=wc[i-1]+wc[i];
 for i:=n-1 downto 0 do
 begin
  dec(wc[x[i]]);
  sa[wc[x[i]]]:=i;
 end;
 
 j:=1; p:=1;
 while p<n do
 begin
  p:=0;
  for i:=n-j to n-1 do
  begin
   y[p]:=i; inc(p);
  end;
  for i:=0 to n-1 do
   if sa[i]>=j then begin y[p]:=sa[i]-j; inc(p); end;
 // for i:=0 to n-1 do writeln(y[i]);
  for i:=0 to n-1 do wd[i]:=x[y[i]];
  for i:=0 to m do wc[i]:=0;
  for i:=0 to n-1 do inc(wc[wd[i]]);
  for i:=1 to m do wc[i]:=wc[i-1]+wc[i];
  for i:=n-1 downto 0 do
  begin
   dec(wc[wd[i]]);
   sa[wc[wd[i]]]:=y[i];
  end;
 
  for i:=0 to n do swap(x[i],y[i]);
 
  p:=1; x[sa[0]]:=0;
  for i:=1 to n-1 do
  begin
   if cmp(sa[i-1],sa[i],j) then x[sa[i]]:=p-1
    else begin x[sa[i]]:=p; inc(p); end;
  end;
 
  j:=j*2;
  m:=p;
 end;
end;
 
 
begin
  assign(input,'bzoj1031r.in'); reset(input);
  assign(output,'bzoj1031r.out'); rewrite(output);
 while not eoln do
 begin
  read(tmp);
  inc(n);
  ch[n]:=tmp;
 end;
 for i:=1 to n do a[i-1]:=ord(ch[i]);
 for i:=n to n*2-1 do a[i]:=a[i-n];
 n:=n*2+1; m:=300;
 getsa;
 for i:=1 to n-1 do
  if sa[i]<(n>>1) then
  begin
   if sa[i]=0 then write(chr(a[n-2]))
    else write(chr(a[sa[i]-1]));
  end;
 close(input);
close(output);
 
 
end.