Coin Flip
In a row of four squares, place a penny, nickel, dime, quarter -
from left to right. The object is to reverse their order - that is,
to get them in the sequence quarter, dime, nickel, penny - in the
fewest possible turns. In each turn, move a coin one square to the
left or right. You may move a coin only into an empty square or onto
an adjacent coin of higher value (e.g., a penny can move onto a
nickel, but not vice versa.) Only the top coin of a stack may move.
What is the smallest number of turns necessary to effect the switch?
Source: Will Shortz, Games Magazine, August 1992.
Used as Ken's POTD 9/6/94.
Solution:
Many people (listed below) turned in the following 22 turn solutions
(which are mirror images of each other), so I assume they are the best:
NRR DL NLL QL NRR PRRR DL QL DRR QL DL PLL NL PRR
PRR NL PLL DL QL DRR QL DL PRRR NRR QL NLL DL NRR
Solutions:
Lynne Onitsuka
Andy Barr
Pete Duisenberg
Stan Witherspoon
(Ken Duisenberg)
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