Here
are two solutions to the problem described in the fourth hint. In
each move, the pair must touch a coin. A minimum of five moves is
needed to solve this variation of the problem.
| 1
A 2 B 3 |
1
A 2 B 3 |
| 1
A · · 3 2 B |
2
B 3 1 A |
| 3
2 B 1 A |
3
1 A 2 B |
| 3
· · 1 A 2 B |
3
· · 2 B 1 A |
| 3
A 2 1 · · B |
3
B 1 2 · · A |
| 2
1 3 A B |
1
2 3 B A |