var
  a: array[1..maxn, 1..maxn] of Integer;
  b: array[1..maxn] of Integer; {b[i]指顶点i到源点的最短路径}
  mark: array[1..maxn] of Boolean;

procedure bhf;
var
  best, best_j: Integer;
begin
  FillChar(mark, SizeOf(mark), false);
  mark[1] := true;
  b[1] := 0;{1为源点}
  repeat
    best := 0;
    for i := 1 to n do
      if mark[i] then {对每一个已计算出最短路径的点}
        for j := 1 to n do
          if (not mark[j]) and (a[i, j] > 0) then
            if (best = 0) or (b[i] + a[i, j] < best) then
            begin
              best := b[i] + a[i, j];
              best_j := j;
            end;
    if best > 0 then
    begin
      b[best_j] := best；mark[best_j] := true;
    end;
  until best = 0;
end;
//delphi/6606