BZOJ1875: [SDOI2009]HH去散步

 1 const p=45989;
 2 type matrix=array[0..200,0..200] of int64;
 3 var a,b:matrix;
 4     c:array[0..1000] of record x,y:longint;end;
 5     i,j,n,m,x,y,s,t,dist,ans,mm:longint;
 6 procedure init;
 7  begin
 8    readln(n,m,dist,s,t);mm:=m<<1-1;
 9    for i:=0 to m-1 do
10     begin
11       readln(x,y);
12       c[i<<1].x:=x;c[i<<1].y:=y;
13       c[i<<1+1].x:=y;c[i<<1+1].y:=x;
14     end;
15  end;
16 procedure mul(var x,y,z:matrix);
17  var t:matrix;i,j,k:longint;
18  begin
19    fillchar(t,sizeof(t),0);
20    for i:=0 to mm do
21      for j:=0 to mm do
22        for k:=0 to mm do
23         t[i,j]:=(t[i,j]+x[i,k]*y[k,j]) mod p;
24    z:=t;
25  end;
26 
27 procedure ksm(cs:longint);
28  begin
29    while cs>0 do
30     begin
31       if cs and 1=1 then mul(a,b,b);
32       cs:=cs>>1;
33       mul(a,a,a);
34     end;
35  end;
36 
37 procedure main;
38  begin
39    fillchar(a,sizeof(a),0);
40    for i:=0 to mm do
41     for j:=0 to mm do
42      if (i<>j) and (i xor 1<>j) and (c[i].y=c[j].x) then
43       inc(a[i,j]);
44    for i:=0 to mm do b[i,i]:=1;
45    ksm(dist-1);
46    ans:=0;
47    for i:=0 to mm do
48     for j:=0 to mm do
49      if (c[i].x=s) and (c[j].y=t) then ans:=(ans+b[i,j]) mod p;
50    writeln(ans);
51  end;
52 
53 begin
54   assign(input,‘input.txt‘);assign(output,‘output.txt‘);
55   reset(input);rewrite(output);
56   init;
57   main;
58   close(input);close(output);
59 end.