question: public static String convertToTitle ( int n ) { if ( n <= 0 ) return "" ; StringBuilder title = new StringBuilder ( ) ; while ( n > 0 ) { n -- ; int r = n % 26 ; title . insert ( 0 , ( char ) ( 'A' + r ) ) ; n = n / 26 ; } return title . toString ( ) ; }
target:  Get the remainder in each loop It should be the last digit Note that the map shall have 1 offset