procedure floyed;
begin
  for I := 1 to n do
    for j := 1 to n do
      if a[I, j] > 0 then
        p[I, j] := I
  else
    p[I, j] := 0;    {p[I,j]表示I到j的最短路径上j的前驱结点}
  for k := 1 to n do {枚举中间结点}
    for i := 1 to n do
      for j := 1 to n do
        if a[i, k] + a[j, k] < a[i, j] then
        begin
          a[i, j] := a[i, k] + a[k, j];
          p[I, j] := p[k, j];
        end;
end;
//delphi/6607