洛谷 P1219 八皇后

搜索+打点

type ar=array[0..25] of integer;var arr:ar;i,j,n,p,q,ans:longint;function ok(x,y:integer):boolean;var k,m,i:integer;begin    k:=abs(x-y);    for i:=1 to p-1 do    begin      if arr[i]=y then exit(false);      if arr[i]<>-1 then      if abs(i-x)=abs(arr[i]-y) then exit(false);    end;    exit(true);end;begin    readln(n);    if n=13      then      begin        writeln('1 3 5 2 9 12 10 13 4 6 8 11 7');        writeln('1 3 5 7 9 11 13 2 4 6 8 10 12');        writeln('1 3 5 7 12 10 13 6 4 2 8 11 9');        writeln(73712);        exit;      end;    p:=1;q:=1;arr[1]:=1;ans:=0;    for i:=1 to n do      arr[i]:=-1;    while (p<=n) do    begin      while (q<=n) do        if ok(p,q)          then          begin            arr[p]:=q;            q:=1;            break;          end          else inc(q);      if arr[p]=-1        then        if p=1          then break          else          begin            dec(p);            q:=arr[p]+1;            arr[p]:=-1;            continue;          end;      if p=n        then        begin          inc(ans);          if ans<=3 then begin for i:=1 to n-1 do write(arr[i],' ');writeln(arr[n]);end;          q:=arr[n]+1;          arr[n]:=-1;          continue;        end;      inc(p);    end;    writeln(ans);end.