(This article was first published on CYBAEA Data and Analysis, and kindly contributed to Rbloggers)
David posts a question about how to solve this knapsack problem using the R statistical computing and analysis platform. My reply in the comments seems to have disappeared for a while so here is my proposed solution. See David’s blog for my earlier proposed solution with a very common error.
## http://blog.revolutioncomputing.com/2009/07/becauseitsfridaytheknapsackproblem.html appetizer.solution < local ( function (target) { app < c(2.15, 2.75, 3.35, 3.55, 4.20, 5.80) r < 2L repeat { c < gtools::combinations(length(app), r=r, v=app, repeats.allowed=TRUE) s < rowSums(c) if ( all(s > target) ) { print("No solution found") break } x < which( abs(starget) < 1e4 ) if ( length(x) > 0L ) { cat("Solution found: ", c[x,], "\n") break } r < r + 1L } }) appetizer.solution(15.05) # Solution found: 2.15 3.55 3.55 5.8
Brute force works, it just doesn’t scale well. (Note that 7×2.15 is another solution.)
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