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100 Problems & Solutions Trang 63

dd[i,j] := 0;
If dd[i,j-1] = 0 then Xetbot(i,j-1);
If dd[i,j+1] = 0 then Xetbot(i,j+1);
If dd[i-1,j] = 0 then Xetbot(i-1,j);
If dd[i+1,j] = 0 then Xetbot(i+1,j);
End;

Procedure Xethangcot( ii : integer );
Var i ,j :integer;
Begin
i := qi[ii];
j := qj[ii];
Inc(hang[i]);
If hang[i] = 1 then Dec(hangthieu);
Inc(cot[j]);
If cot[j] = 1 then Dec(cotthieu);
End;

Procedure Xetlaihangcot( ii : integer );
Var i,j : integer;
Begin
i := qi[ii];
j := qj[ii];
If hang[i] = 1 then Inc(hangthieu);
Dec(hang[i]);
If cot[j] = 1 then Inc(cotthieu);
Dec(cot[j]);
End;

Procedure Duyet( i : integer;last : integer );
Var ii :integer;
Begin
If i > n then
begin thughinhancauhinh; exit; end;
For ii := last + 1 to sl do
begin
themdiem(ii);
xethangcot(ii);
If hangthieu + cotthieu <= n - i then duyet(i+1,ii);
Xetlaihangcot(ii);
bodiem(ii);
end;
End;

Procedure Duyetcauhinh( i ,j : integer );
Var jj : integer;
Begin
sh := i;
sc := j;
FillChar(hang ,SizeOf(hang),0);

Tin học & Nhà trường 100 Đề Toán - Tin học