Copyright ©1997 by Paul Niquette. All rights reserved. |
t was convenient for our analysis in this puzzle that the Soviets chose names of towns near their launch complexes such that we may substitute A, B, C, D for their abbreviations. Also, the use of 0 and 1 may have mnemonic value, representing OUT and IN for the instantaneous placement of missiles. Thus...
Sophisticated solvers will recognize
that particular sequence
for postulating Soviet missile movements as "reflected
binary." The right-most
non-zero columns reflect vertically the binary values
in the table above
the (2n)th
entry. Huh? Reflected
binary is but one of many families of coding sequences
by which only a
single bit is changed at each step. One of them meets
the conditions of
the problem..
Thus, assuming that the Soviets wanted to distribute the moves uniformly among their missiles, they would have chosen a sequence as indicated in the table. {HyperNote}
n the early sixties, this "state assignment" solution was discovered during the logical design of a peripheral controller and came to be called a "Niquette Counter." It exploited the observation that for a finite automaton with 2n states, uniform state transitions can be made only when 2n is divisible by n. That does not happen as often as one might think.
Now that you have seen the solution, you might try starting with a blank table and creating your own Niquette Counter. Care to guess how many there are? Finally, suppose that U.S. spy satellites discovered extra roadways being built by the Russians, such that squadrons of MY missiles could be moved into and out of their respective launch sites up to three at a time. Sophisticated solvers might enjoy strategizing retrospcctively on behalf of the Kremlin, with the objective of maximizing the security of the MY missiles while still assuring that all weapons are moved in equal amounts. {Return} |
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