数独杀手

type
  c=array[1..9]of boolean;
var
  a:array[1..9,1..9]of longint;
  b:array[1..9,1..9]of boolean;
  ok:c;
  o:array[1..81]of record i,j:longint; end;
  i,j,num,ci,cj:longint;
procedure dfs(d:longint;ok:c);
var i,j,k,x,y:longint;
begin
  if d=num+1 then
    begin
      for i:=1 to 9 do
        begin
          for j:=1 to 9 do write(a[i,j],‘ ‘);
          writeln;
        end;
      halt;
    end;
  x:=o[d].i;  y:=o[d].j;
  for i:=1 to 9 do ok[i]:=true;
  for j:=1 to 9 do if (b[x,j])then ok[a[x,j]]:=false;//行和列
  for i:=1 to 9 do if (b[i,y])then ok[a[i,y]]:=false; 
  ci:=((x-1) div 3)*3+1;   cj:=((y-1) div 3)*3+1;  //九宫格
  for i:=ci to ci+2 do
    for j:=cj to cj+2 do if (b[i,j]) then ok[a[i,j]]:=false;
  for k:=1 to 9 do
    if ok[k] then
    begin
      a[x,y]:=k;

      b[x,y]:=true;
      dfs(d+1,ok);
      b[x,y]:=false;
    end;
end;
begin
  assign(input,‘math.in‘);  assign(output,‘math.out‘);
  reset(input);  rewrite(output);
  for i:=1 to 9 do
    for j:=1 to 9 do
      begin
        b[i,j]:=true;
        read(a[i,j]);
        if a[i,j]=0 then
          begin
            b[i,j]:=false;
            inc(num);
            o[num].i:=i;  o[num].j:=j;
          end;
      end;
  dfs(1,ok);
  close(input);  close(output);
end.