麻烦各位dalao来看看吧，我代码里有解释的QAQ

var
  bi:boolean;
  t,a1,a2,num,tot,head,tail:longint;
  s1,s2,s3:char;
  i,j,m,n,k,p:longint;
  map:array[0..30,0..30]of boolean;
  ru,s:array[0..30]of longint;
  f:array[0..300]of longint;
begin
  readln(n,m);
  bi:=false;
  while m<>0 do
    begin
      dec(m); inc(t);//记录这是第几个关系
      readln(s1,s2,s3);
      a1:=ord(s1)-64; a2:=ord(s3)-64;
      map[a1,a2]:=true;//邻接矩阵存图
      inc(ru[a2]);//记录每个点的入度

      head:=0; tail:=0; tot:=0; num:=0;
      for i:=1 to n do
        if ru[i]=0 then
          begin
            inc(tail); f[tail]:=i;
            inc(tot); inc(num);
            {tot记的是访问了几个点
             num记的是有几个入度为0的点，如果有多个就还没确定数列对吧}
          end;

      for i:=1 to n do s[i]:=ru[i];//拓扑的临时数组
      while head<tail do
        begin
          inc(head);
          for i:=1 to n do
            if map[f[head],i]=true then
              begin
                dec(s[i]);
                if s[i]=0 then
                  begin
                    inc(tail); f[tail]:=i; inc(tot);
                  end;
              end;
        end;

      if tot<n then//如果不是所有点都被访问了，就说明有环对吧
        begin
          writeln('Inconsistency found after ',t,' relations.');
          exit;
        end;
      if (tot=n)and(num=1) then
        begin
          write('Sorted sequence determined after ',t,' relations: ');
          for i:=1 to tail do write(chr(f[i]+64));
          writeln;
          exit;
        end;
    end;
  writeln('Sorted sequence cannot be determined.');
end.