Moving Counter Puzzles 135when you will have the first two counters properly placed. The puzzle is to
determine the fewest possible exchanges in which this can be done.- NINE MEN IN A TRENCH
Here are nine men in a trench. Number I is the sergeant, who wishes
to place himself at the other end of the line-at point I-all the other men
returning to their proper places as at present. There is no room to pass in the
trench, and for a man to attempt to climb over another would be a dangerous
exposure. But it is not difficult with those three recesses, each of which will
hold a man.How is it to be done with the fewest possible moves? A man may go any
distance that is possible in a move.- BLACK AND WHITE
One morning Rackbrane showed his friends this old puzzle. Place four
white and four black counters alternately in a row as here shown. The puzzle
is to transfer two contiguous counters to one end then move two contiguous
counters to the vacant space, and so on until in four such moves they form a
continuous line of four black counters followed by four white ones. Remem-
ber that two counters moved must always be contiguous ones.
"Now," he said, "as you know how to do that, try this variation. The con-
ditions are exactly the same, only in moving a contiguous pair you must
make them change sides. Thus, if you move 5, 6, to the end, you must replace
them in the order 6, 5. How many moves will you now require?"