if previous character is '0' than we put both '1' and '0' at end of string example str = "00" then new string "001" and "000"
if ( str [ n - 1 ] == '0' ) : NEW_LINE INDENT str [ n ] = '0' NEW_LINE generateAllStringsUtil ( K , str , n + 1 ) NEW_LINE str [ n ] = '1' NEW_LINE generateAllStringsUtil ( K , str , n + 1 ) NEW_LINE DEDENT