Lơi giải Bài 3 - Tin học trẻ-PP Quay lui

uses crt;
const nm=100;
Type td=array[1..nm] of byte;
var x,y,L,a,a2:td;
Max:word;
chon:array[1..nm] of boolean;
n,k,i,dd,count,count2:word;
Procedure doc_tep;
Var f: text;
Begin
assign(f,'ech.inp');
reset(f);
readln(f,n,k);
for i:=1 to n do readln(f,x[i],y[i],L[i]);
close(f);
End;
procedure try(i:byte);
var j:byte;
Begin
for j:=2 to n do
if (dd>=k) and (not chon[j]) and
((((x[j]=x[a[i-1]]) and (y[j]>y[a[i-1]])) or ((y[j]=y[a[i-1]]) and
(x[j]>x[a[i-1]])))) then
begin
a[i]:=j; dd:=dd+L[j]-k; count:=count+1;
chon[j]:=true;
if a[i]=n then
Begin if Max<dd then begin max:=dd; a2:=a; count2:= count; end end
else try(i+1);
chon[j]:=false; dd:=dd-L[j]+k; count:=count-1;
end;

end;
Procedure ghi_tep;
Var f: text;
Begin
assign(f,'ech.out');
rewrite(f);
writeln(f,max);
writeln(f,count2);
for i:=1 to count2 do writeln(f,x[a2[i]],' ',y[a2[i]]);
close(f);
End;
Procedure thuc_hien;
Begin
Doc_tep;
Max:=0; a[1]:=1; dd:=L[1]; count:=1;
fillchar(chon,sizeof(chon),0);
try(2);
ghi_tep;
End;
Begin
clrscr;
thuc_hien;
End.