## reverse3

Author: Stuart Reges (on 2020/10/08)

Write a method reverse3 that reverses each successive sequence of 3 values in a list of integers. For example, suppose that a variable list stores:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]

and we make the following call:

list.reverse3();

Afterwards the list should store the following sequence of values:

[3, 2, 1, 6, 5, 4, 9, 8, 7, 12, 11, 10, 15, 14, 13]

The first sequence of 3 values (1, 2, 3) has been reversed to be (3, 2, 1). The second sequence of 3 values (4, 5, 6) has been reverse to be (6, 5, 4). And so on. If the list has extra values that are not part of a sequence of 3, those values are unchanged. For example, if the list had instead stored:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]

The result would have been:

[3, 2, 1, 6, 5, 4, 9, 8, 7, 12, 11, 10, 15, 14, 13, 16, 17]

Notice that the values (16, 17) are unchanged in position.

The list will not always contain sequential integers. The following list:

[3, 8, 19, 42, 7, 26, 19, -8, 193, 204, 6, -4, 99]

would be rearranged as follows:

[19, 8, 3, 26, 7, 42, 193, -8, 19, -4, 6, 204, 99]

Your method should not change the list if it has fewer than three values.