Slow Solution
-------------

The most straightforward solution is to do the following:

In the event of a raise, automatically give everyone a raise.
In the event of a query, compute the minimum and maximum salaries on demand.

This will give us a linear-time update and a linear-time query, which will be
too slow for our needs.

Optimizations
-------------

One small optimization to note is that a raise does not necessarily need to
be applied immediately. If you have a lot of raises happening at once, you can
mark that you need to give out raises but not actually give them out until a
query has to happen.

Another one is to precompute the minimum and maximum salaries for employees, so
that queries can take constant time instead of linear time.

Full Solution
-------------

Instead of striving for a constant-time update or constant-time query, we will
instead go for a logarithmic-time update and query.

We start by reassigning IDs to all employees by doing a pre-order traversal of
the tree. Note that for any employee, all of the IDs of that employee's
subordinates form a contiguous interval.

With this, we can now maintain all salaries in a range tree that supports
range increment and min/max range query, both of which are operations that run
in logarithmic time.