The Four Elopements : Solution

The feat can be performed in 17 trips.

We begin with ABCD (the men) and abcd (the girls) all on shore. The following chart is self-explanatory.

	Shore	Island	Other side
1	A B C D c d		a b
2	A B C D b c d		a
3	A B C D d	b c	a
4	A B C D c d	b	a
5	C D c d	b	A B a
6	B C D c d	b	A a
7	B C D	b c d	A a
8	B C D d	b c	A a
9	D d	b c	A B C a
10	D d	a b c	A B C
11	D d	b	A B C a c
12	B D d	b	A C a c
13	d	b	A B C D a c
14	d	b c	A B C D a
15	d		A B C D a b c
16	c d		A B C D a b
17			A B C D a b c d

Note: There are other ways the puzzle can be solved in 17 trips. This solution is the most satisfactory in that it involves the fewest "gettings in" and "gettings out".