This particular task is not a problem about R. It is a problem n combinatorics. Start with the obvious brute force algorithm (1) Let S be the union of all the sets (2) For each K in 0 .. |S| (3) Enumerate all |S| choose K subsets C of S (4) If C satisfies the condition, report it and stop (5) Report that there is no solution. There is a function 'combn' in the 'combinat' package that is perfectly suited to step 3.
I have not examined your outlined solution. Even if it is right, it pays to START by writing a crude obvious brute force algorithm like this so that you can test your test cases. On Fri, 6 Dec 2019 at 03:14, Александр Дубровский <dubrovvssk...@gmail.com> wrote: > > Task: > A family of sets of letters is given. Find K for which one can construct a > set consisting of K letters, each of them belonging to exactly K sets of a > given family. > > Possible solution: > For each letter, we will have a separate 'scoop', in which we will' put ' > the letter. This can be done using array A of 255 elements. In this case, > the number of the 'scoop' corresponding to a letter is determined by the > letter code (it is known that any letter is encoded by some binary number > containing 8 digits - called bits; in Pascal, its code can be determined by > using the ord function). When viewing the sets, let's count how many times > each letter met. This is done as follows. When you meet a letter, increase > the contents of the corresponding array element by 1. The initial contents > of the array elements are 0. After viewing the letters of all sets, > elements a determine the number of corresponding letters, and therefore the > number of sets that have the corresponding letter (because in one set, all > elements are different!). Using similarly array B from 255 elements (more > need not, so as the desired the number of to on condition not exceeds > number of letters) count the number of units, twos and so on in array A. > Maximum significance index K, for which K=B[K] and will solution meet the > tasks. > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
