【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=200419;
var
 c,h,rank,sa,x,y,stack:array[0..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:=1;
 while p<n do
  begin
   fillchar(c,sizeof(c),0);
   for i:= 1 to n-p do y[i]:=rank[i+p];
   for i:= n-p+1 to n do y[i]:=0;
   for i:= 1 to n do inc(c[y[i]]);
   for i:= 1 to n do inc(c[i],c[i-1]);
   for i:= 1 to n do
    begin
     sa[c[y[i]]]:=i;
     dec(c[y[i]]);
    end;
   fillchar(c,sizeof(c),0);
   for i:= 1 to n do x[i]:=rank[i];
   for i:= 1 to n do inc(c[x[i]]);
   for i:= 1 to n do inc(c[i],c[i-1]);
   for i:= n downto 1 do
    begin
     y[sa[i]]:=c[x[sa[i]]];
     dec(c[x[sa[i]]]);
    end;
   for i:= 1 to n do sa[y[i]]:=i;
   tot:=1;
   rank[sa[1]]:=1;
   for i:= 2 to n do
    begin
     if (x[sa[i]]<>x[sa[i-1]]) or (x[sa[i]+p]<>x[sa[i-1]+p]) then inc(tot);
     rank[sa[i]]:=tot;
    end;
   p:=p<<1;
  end;
 for i:= 1 to n do sa[rank[i]]:=i;
end;

procedure makeh(s:ansistring);
var i,j,p:longint;
begin
 h[1]:=0; p:=0;
 for i:= 1 to n do
  begin
   p:=max(p-1,0);
   if rank[i]=1 then continue;
   j:=sa[rank[i]-1];
   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:= 1 to n do c[i]:=0;
 for i:= 1 to n do x[i]:=ord(s[i]);
 for i:= 1 to n do inc(c[x[i]]);
 for i:= 1 to 122 do inc(c[i],c[i-1]);
 for i:= 1 to n do
  begin
   sa[c[x[i]]]:=i;
   dec(c[x[i]]);
  end;
 rank[sa[1]]:=1;
 tot:=1;
 for i:= 2 to n do
  begin
   if x[sa[i]]<>x[sa[i-1]] then inc(tot);
   rank[sa[i]]:=tot;
  end;
 fillchar(x,sizeof(x),0);
 fillchar(y,sizeof(y),0);
 make;
 makeh(s);
end;

function calc(s:ansistring):int64;
var ctb,i,m,ht,top:longint;
 ans:int64;
begin
 ans:=0;
 init(s);
 h[0]:=k-1; h[n+1]:=k-1;
 top:=0; i:=1;
 stack[0]:=0;
 while i<=n+1 do
  begin
   ht:=h[stack[top]];
   if ((h[i]<k) and (top=0)) 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]+1;
       if (h[i]>=k) and (h[i]>h[stack[top-1]]) then
        begin
         ctb:=ht-h[i];
         h[stack[top]]:=h[i];
        end
       else
        begin
         ctb:=ht-h[stack[top-1]];
         dec(top);
        end;
       inc(ans,(int64(m)*int64(m-1) div 2) *int64(ctb));
      end
  end;
 exit(ans);
end;

Begin
 readln(k);
 while k<>0 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.