Le Monde puzzle [1]

January 10, 2011

(This article was first published on Xi'an's Og » R, and kindly contributed to R-bloggers)

Following the presentation of the first Le Monde puzzle of the year, I tried a simulated annealing solution on an early morning in my hotel room. Here is the R code, which is unfortunately too rudimentary and too slow to be able to tackle n=1000.

#minimise sum_{i=1}^I x_i
#for 1le x_ile 2n+1, 1e ile I
#    Ige n, x_i ne x_j
#    a=x_i,b=x_j,i,jin I implies a+b=x_k for a kin I




 if (tempe*log(runif(1))

The solution to the puzzle (given in the next Le Monde issue) is to take only the even digits, resulting in a minimum sum equal to n(n+1).

Filed under: R, Statistics Tagged: Le Monde, mathematical puzzle, simulated annealing

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