fork download
copy 
  1. uses    math;
  2. const   fi='';
  3.         fo='';
  4.         maxn=300;
  5.         maxm=maxn*maxn;
  6.         oo=trunc(1e9);
  7. type    Tq      =record
  8.                 u1,u2,k :longint;
  9.                 end;
  10. var     q       :array[1..2*maxn*maxn*10] of Tq;
  11.         cx      :array[1..maxn,1..maxn,1..2] of boolean;
  12.         f       :array[1..maxn,1..maxn,1..2] of longint;
  13.         i,j,n,m,s,t     :longint;
  14.         dau,cuoi,res    :longint;
  15.         // danh sach
  16.         link,head,ke    :array[1..maxm] of longint;
  17. procedure enter;
  18. var     u,v     :longint;
  19. begin
  20.         assign(input,fi);reset(input);
  21.         readln(n,m,s,t);
  22.         for i:=1 to m do
  23.                 begin
  24.                         read(u,v);
  25.                         link[i] := head[u];
  26.                         head[u] :=i;
  27.                         ke[i] := v;
  28.                 end;
  29.         close(input);
  30. end;
  31. procedure push(x,y,z:longint);
  32. begin
  33.         inc(cuoi);
  34.         q[cuoi].u1:=x;
  35.         q[cuoi].u2:=y;
  36.         q[cuoi].k:=z;
  37. end;
  38. procedure process;
  39. var     v1,v2,u1,u2,k :longint;
  40. begin
  41.         dau :=1; cuoi :=0;
  42.         push(s,t,1);
  43.         fillchar(cx,sizeof(cx),true);
  44.         //
  45.         for i:=1 to n do
  46.                 for j:=1 to n do
  47.                         for k:=1 to 2 do
  48.                                 f[i,j,k] := oo;
  49.         f[s,t,1] := 0;
  50.         while dau<=cuoi do
  51.                 begin
  52.                         u1 := q[dau].u1;
  53.                         u2 := q[dau].u2;
  54.                         k := q[dau].k;
  55.                         inc (dau);
  56.                         if k=1 then
  57.                                 begin
  58.                                         i := head[u1];
  59.                                         while i>0 do
  60.                                                 begin
  61.                                                         v1 := ke[i];
  62.                                                         if cx[v1,u2,2] then
  63.                                                           begin
  64.                                                                 f[v1,u2,2] := min(f[v1,u2,2],f[u1,u2,1]+1);
  65.                                                                 push(v1,u2,2);
  66.                                                                 cx[v1,u2,2] := false;
  67.                                                           end;
  68.                                                         i:= link[i];
  69.                                                 end;
  70.                                 end;
  71.                         if k=2 then
  72.                                 begin
  73.                                         i := head[u2];
  74.                                         while i>0 do
  75.                                                 begin
  76.                                                         v2 := ke[i];
  77.                                                         if cx[u1,v2,1] then
  78.                                                           begin
  79.                                                                 f[u1,v2,1] := min(f[u1,u2,2]+1,f[u1,v2,1]);
  80.                                                                 push(u1,v2,1);
  81.                                                                 cx[u1,v2,1] := false;
  82.                                                           end;
  83.                                                         i:= link[i];
  84.                                                 end;
  85.                                 end;
  86.                 end;
  87.         res := oo;
  88.         for i:=1 to n do
  89.                 res := min(res,f[i,i,1]);
  90. end;
  91. procedure print;
  92. begin
  93.         assign(output,fo);rewrite(output);
  94.         if res=oo then write(-1) else write(res div 2);
  95.         close(output);
  96. end;
  97. begin
  98.         enter;
  99.         process;
  100.         print;
  101. end.
Success #stdin #stdout 0s 23624KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
-1
https://ideone.com/iMjsRu
language:
Pascal (fpc 3.0.4)
created:
6 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!