Đề thi Toán - Tin học trong nhà trường (Bài 56)

Bài 56/2001 - Chia lưới
(Dành cho học sinh PTTH)
Program Chia_luoi ;
Uses Crt ;
Const Fi = `LUOI.INP`;
Fo = `LUOI.OUT`;
Var A : Array[1..20,1..20]Of Integer ;
B : Array[1..20,1..20]Of 0..1 ;
Px,Py: Array[1..4] Of ShortInt ;
M,N,S,S1,S2 : LongInt ;
F : Text ;
Procedure Read_Input ;
Var i,j :Integer;
Begin
Clrscr ; S:= 0 ;
Assign(F,Fi) ;Reset(F) ;
Readln(F,M,N);
For i:=1 to M do
Begin
For j:=1 to N do
Begin
Read(F,A[i,j]);
S:=S+A[i,j];
End;
Readln(F);
End;
Close(F);
End;

Procedure Innit ;
Begin
S1 := S div 2;
Px[1]:= 0 ;Px[2]:= 0 ;Px[3]:=1 ;Px[4]:=-1 ;
Py[1]:= 1 ;Py[2]:=-1 ;Py[3]:=0 ;Py[4]:= 0 ;
End ;

Procedure Write_Output ;
Var i,j :Integer;
Begin
Assign(F,Fo); ReWrite(F);
For i:=1 to M do
Begin
For j:=1 to N do
Write(F,B[i,j],` `);
Writeln(F);
End;
Close(F);Halt;
End;

Function Ktra(x,y : Integer) : Boolean ;
Begin
Ktra:= False ;
If (x in [1..M]) And (y in [1..N]) And
(B[x,y] = 0 ) Then Ktra := True ;
End;

Procedure Try(x,y:Integer ;Sum :LongInt);
Var i :Integer ;
Begin
For i:=1 to 4 do
If Ktra(x+Px[i],y+Py[i]) Then
Begin
x := x + Px[i] ;
y := y + Py[i] ;
Sum := Sum + A[x,y];
B[x,y] := 1;
If Sum = S2 Then Write_Output ;
Try(x,y,Sum) ;
Sum := Sum - A[x,y];
B[x,y] := 0;
x := x - Px[i] ;
y := y - Py[i] ;
End ;
End;

Procedure Run ;
Var i,j : Integer ;
Begin
Read_Input ;Innit ;
For i:=1 to M do
For j:=1 to N do
If A[i,j]>= S1 Then
Begin
Fillchar(B,SizeOf(B),0);
B[i,j]:=1;
Write_Output;
End ;
For S2 := S1 downto 1 do
Begin
Fillchar(B,SizeOf(B),0);
B[1,1]:=1;
Try(1,1,A[1,1]);
End;
End;

BEGIN
Run;
END.
(Lời giải của bạn Lê Sơn Tùng - Vĩnh Phúc )