【POJ3415】 Common Substrings (SA+单调栈)

这道是求长度不小于 k 的公共子串的个数...很不幸，我又TLE了...

解法参考论文以及下面的链接

http://www.cnblogs.com/vongang/archive/2012/11/20/2778481.html

http://hi.baidu.com/fpkelejggfbfimd/item/5c76cfcba28fba26e90f2ea6

 const maxn=;
 var
  c,h,rank,sa,x,y,stack:array[..maxn] of longint;
  n,k,top:longint;
  a,b,d:int64;
  s1,s2:ansistring;
 
 function max(x,y:longint):longint; begin if x>y then exit(x) else exit(y); end;
 function min(x,y:longint):longint; begin if x<y then exit(x) else exit(y); end;
 
 procedure make;
 var p,i,tot:longint;
 begin
  p:=;
  while p<n do
   begin
    fillchar(c,sizeof(c),);
    for i:=  to n-p do y[i]:=rank[i+p];
    for i:= n-p+ to n do y[i]:=;
    for i:=  to n do inc(c[y[i]]);
    for i:=  to n do inc(c[i],c[i-]);
    for i:=  to n do
     begin
      sa[c[y[i]]]:=i;
      dec(c[y[i]]);
     end;
    fillchar(c,sizeof(c),);
    for i:=  to n do x[i]:=rank[i];
    for i:=  to n do inc(c[x[i]]);
    for i:=  to n do inc(c[i],c[i-]);
    for i:= n downto  do
     begin
      y[sa[i]]:=c[x[sa[i]]];
      dec(c[x[sa[i]]]);
     end;
    for i:=  to n do sa[y[i]]:=i;
    tot:=;
    rank[sa[]]:=;
    for i:=  to n do
     begin
      if (x[sa[i]]<>x[sa[i-]]) or (x[sa[i]+p]<>x[sa[i-]+p]) then inc(tot);
      rank[sa[i]]:=tot;
     end;
    p:=p<<;
   end;
  for i:=  to n do sa[rank[i]]:=i;
 end;
 
 procedure makeh(s:ansistring);
 var i,j,p:longint;
 begin
  h[]:=; p:=;
  for i:=  to n do
   begin
    p:=max(p-,);
    if rank[i]= then continue;
    j:=sa[rank[i]-];
    while (i+p<=n) and (j+p<=n) and (s[i+p]=s[j+p]) do inc(p);
    h[rank[i]]:=p;
   end;
 end;
 
 procedure init(s:ansistring);
 var i,tot:longint;
  ch:char;
 begin
  n:=length(s);
  for i:=  to n do c[i]:=;
  for i:=  to n do x[i]:=ord(s[i]);
  for i:=  to n do inc(c[x[i]]);
  for i:=  to  do inc(c[i],c[i-]);
  for i:=  to n do
   begin
    sa[c[x[i]]]:=i;
    dec(c[x[i]]);
   end;
  rank[sa[]]:=;
  tot:=;
  for i:=  to n do
   begin
    if x[sa[i]]<>x[sa[i-]] then inc(tot);
    rank[sa[i]]:=tot;
   end;
  fillchar(x,sizeof(x),);
  fillchar(y,sizeof(y),);
  make;
  makeh(s);
 end;
 
 function calc(s:ansistring):int64;
 var ctb,i,m,ht,top:longint;
  ans:int64;
 begin
  ans:=;
  init(s);
  h[]:=k-; h[n+]:=k-;
  top:=; i:=;
  stack[]:=;
  while i<=n+ do
   begin
    ht:=h[stack[top]];
    if ((h[i]<k) and (top=)) or (h[i]=ht) then inc(i)
     else if h[i]>ht then begin inc(top);stack[top]:=i; inc(i); end
      else
       begin
        m:=i-stack[top]+;
        if (h[i]>=k) and (h[i]>h[stack[top-]]) then
         begin
          ctb:=ht-h[i];
          h[stack[top]]:=h[i];
         end
        else
         begin
          ctb:=ht-h[stack[top-]];
          dec(top);
         end;
        inc(ans,(int64(m)*int64(m-) div ) *int64(ctb));
       end
   end;
  exit(ans);
 end;
 
 Begin
  readln(k);
  while k<> do
   begin
    readln(s1);
    a:=calc(s1);
    readln(s2);
    b:=calc(s2);
    s1:=s1+'$'+s2;
    d:=calc(s1);
    writeln(d-a-b);
    readln(k);
   end;
 End.