NKOJ 1781: ISBN

2007082601.pas

Var
     a:array[1..10]OF 0..10;
     str:string;
     n,i,s:integer;
Function cal(x,y:integer):integer;
Var
      i:integer;
      ans:integer;
Begin
      ans:=0;
      IF y>=x THEN For i:=x to y do inc(ans,a[i]*(11-i));
      cal:=ans;
End;
Begin
     s:=-1;
     readln(str);
     For i:=1 to 10 Do
      Case str[i] OF
       '0'..'9':a[i]:=ord(str[i])-ord('0');
       'X':a[i]:=10;
       '?':n:=i;
      End;
     IF n=10{如果第十位空缺,那么直接计算}
      THEN s:=11-cal(1,9) mod 11
      ELSE{否则,一一试探}
       For i:=0 to 9 Do
        Begin
          a[n]:=i;
          IF cal(1,10) mod 11=0
           THEN s:=i;
        End;
     IF s=10
      THEN writeln('X')
      ELSE writeln(s);
End.