【POJ2406】Power Strings（KMP，后缀数组）

题意：

n<=1000000，cas较大

思路：这是一道论文题

后缀数组已弃疗，强行需要DC3构造，懒得（不会）写

 var a,x,y,sa,rank,height,dp,wc,wd:array[..]of longint;
     n,m,i,j,len,ans,st:longint;
     ch:ansistring;
     flag:boolean;

 function min(x,y:longint):longint;
 begin
  if x<y then exit(x);
  exit(y);
 end;

 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(n:longint);
 var i,j,p:longint;
 begin
  for i:= to m do wc[i]:=;
  for i:= to n- do
  begin
   x[i]:=a[i];
   inc(wc[a[i]]);
  end;
  for i:= to m- do wc[i]:=wc[i-]+wc[i];
  for i:=n- downto  do
  begin
   dec(wc[x[i]]);
   sa[wc[x[i]]]:=i;
  end;
  j:=; p:=;
  while p<n do
  begin
   p:=;
   for i:=n-j to n- do
   begin
    y[p]:=i; inc(p);
   end;
   for i:= to n- do
    if sa[i]>=j then begin y[p]:=sa[i]-j; inc(p); end;
   for i:= to n- do wd[i]:=x[y[i]];
   for i:= to m- do wc[i]:=;
   for i:= to n- do inc(wc[wd[i]]);
   for i:= to m- do wc[i]:=wc[i-]+wc[i];
   for i:=n- downto  do
   begin
    dec(wc[wd[i]]);
    sa[wc[wd[i]]]:=y[i];
   end;
   for i:= to n do swap(x[i],y[i]);
   p:=; x[sa[]]:=;
   for i:= to n- do
    if cmp(sa[i-],sa[i],j) then x[sa[i]]:=p-
     else begin x[sa[i]]:=p; inc(p); end;
   j:=j*;
   m:=p;
  end;
 end;

 procedure getheight(n:longint);
 var i,j,k:longint;
 begin
  for i:= to n do rank[sa[i]]:=i;
  k:=;
  for i:= to n- do
  begin
   if k> then dec(k);
   j:=sa[rank[i]-];
   while a[i+k]=a[j+k] do inc(k);
   height[rank[i]]:=k;
  end;
 end;

 {procedure init;
 begin
  fillchar(a,sizeof(a),0);
  fillchar(x,sizeof(x),0);
  fillchar(y,sizeof(y),0);
  fillchar(sa,sizeof(sa),0);
  fillchar(rank,sizeof(rank),0);
  fillchar(height,sizeof(height),0);
  fillchar(dp1,sizeof(dp1),0);
  fillchar(dp2,sizeof(dp2),0);
 end;     }

 begin
  assign(input,'data.in'); reset(input);
  assign(output,'poj2406.out'); rewrite(output);
  while not eof do
  begin
   //init;
   readln(ch);
   n:=length(ch);
   if ch='.' then break;
   for i:= to n do
   begin
    height[i]:=; sa[i]:=; rank[i]:=;
    dp[i]:=;
   end;
   for i:= to n- do a[i]:=ord(ch[i+]);
   a[n]:=; m:=;
   getsa(n+);
   getheight(n);
   dp[rank[]]:=maxlongint;
   for i:=rank[]+ to n do dp[i]:=min(height[i],dp[i-]);
   for i:=rank[]- downto  do dp[i]:=min(height[i+],dp[i+]);
   ans:=;
   for i:= to n div  do
    if n mod i= then
    begin
     st:=n-i;
     if dp[rank[i]]=n-i then begin ans:=n div i; break; end;
    end;
   writeln(ans);
  end;
 end.

显然钦定的算法是KMP

 var a:ansistring;
     next:array[..]of longint;
     n,i,j:longint;

 begin

  while not eof do
  begin
   readln(a);
   if a='.' then break;
   n:=length(a);
   i:=; j:=;
   next[]:=;
   while j<=n do
   begin
    if (i=)or(a[i]=a[j]) then
    begin
     inc(i); inc(j);
     next[j]:=i;
    end
     else i:=next[i];
   end;
   if n mod (n-next[n+]+)= then
    writeln(n div (n-next[n+]+))
     else writeln();
   for i:= to n+ do next[i]:=;
  end;

 end.