This solution uses three fields: an int
for the hour on a 12-hour clock, an int
for the minute on a 12-hour clock, and a boolean
for the AM/PM indicator (true for AM and false for PM).
The advance method works by calling one
of two private methods. The first private method is able to
advance the time forward by 1 minute accounting for changes
in the hour and AM/PM indicator. The second private method is able to
reverse the time backward by 1 minute accounting for changes
in the hour and AM/PM indicator. advance uses
a loop to call the appropriate method minutes times
where minutes is the number of minutes that
the time should change.
This solution is simple to implement compared to trying to change the time by an arbitrary number of minutes but it is slow if the time changes by a large number of minutes. See solutions 3 and 4 for solutions that do not use a loop.
Note that the constructors, accessor methods,
setHour, and setMinute
are straightforward to implement using this approach,
but advance requires careful attention to
detail to implement correctly.
This solution uses one field, an int
for the number of minutes after midnight. Because
no explicit information is kept about the hour or
AM/PM indicator, this information must be computed
when required.
The advance method begins by making
two observations:
minutes is negative. Observation 2 means
that we can always move the time forward by less than
24 hours and still get the correct time for any value
of minutes.
Because the time is kept in minutes, advance
only needs to add minutes to
this.minute and then ensure
that this.minute is less than the number
of minutes in one day.
Compared to the previous solution,
the constructors, accessor methods,
setHour, and setMinute
are more difficult to implement
but advance is much easier to implement.
In particular, setHour requires careful
attention to whether the current time is in the AM or PM.
This solution uses three fields: an int
for the hour on a 12-hour clock, an int
for the minute on a 12-hour clock, and a boolean
for the AM/PM indicator (true for AM and false for PM).
Without using a loop, this solution computes the final time after advancing the specified number of minutes. Keeping track of the correct number of hours and minutes to advance the time, as well as computing when the hour and AM/PM indicator change is very difficult to do without extensive unit tests.
This solution uses three fields: an int
for the hour on a 12-hour clock, an int
for the minute on a 12-hour clock, and a boolean
for the AM/PM indicator (true for AM and false for PM).
Without using a loop and without using the remainder operator, this solution computes the final time after advancing the specified number of minutes. In the previous solution, it is very tricky to keep track of when the AM/PM indicator needs to change. This solution avoids the AM/PM indicator problem by internally converting the time to a 24-hour clock.