Metoda Backtracking 8 regine

 

Program 8regine;

var x:array[1..100] of byte;
n:byte; nrsol:word;
procedure scriesol;
var i,j:byte;
begin
inc(nrsol);
writeln('Solutia a',nrsol,'este');
for i:=1 to n do begin
writeln;
for j:=1 to n do                                    
 if x[j]=i then write('X',' ')                                              
 else write('O',' ');
end;end;

function potcont(k:byte):boolean;
var i:byte;
atac:boolean;
begin
atac:=false;
for i:=1 to k-1 do
if(x[i]=x[k]) or (k-i=abs(x[k]-x[i])) then atac:=true;
potcont:=not atac;
end;

procedure back(k:byte);
var i:byte;
begin
for i:=1 to n do  
begin
x[k]:=i;
if potcont(k) then
if k=n then scriesol
else back(k+1);
end;
end;

begin
read(n);
nrsol:=0;
back(1);
writeln(nrsol,'solutii');
end.