combinations

问题 Let's say I have the following data frame: ID Code 1 1 A 2 1 B 3 1 C 4 2 B 5 2 C 6 2 D 7 3 C 8 3 A 9 3 D 10 3 B 11 4 D 12 4 B I would like to get the count of unique values of the column "ID" by pairwise combinations of the column "Code": Code.Combinations Count.of.ID 1 A, B 2 2 A, C 2 3 A, D 1 4 B, C 3 5 B, D 3 6 C, D 2 I have searched for solution(s) online, so far haven't been able to achieve the desired result. Any help would be appreciated. Thanks! 回答1: Here is a data.table way to solve

问题 I have to built a function which would list the all possibilities to put +, - or nothing between the numbers ranging from 1 to 9 and print it result. For example: 1+2+3+4+5+6+7+8+9=45, 1+2+3+4+5+6+7+8-9=25, 1+2+3+4+5+6+7+89=117, 1+2+3+45-67+89=73 and so on. While taking care that every expression must have all the numbers present between 1 to 9 also there sequence should be intact. Below is my code to achieve the result but it does not generate all possible combination. $characters = ['+', '-

问题 Lets say I have several sets of options in Javascript var color = ["red", "blue", "green","yellow"]; var size = ["small", "medium", "large"]; var weight = ["heavy", "light"]; what is an efficient algorithm to get all the combinations of these options in an array that looks like this ["red and small and heavy", "red and small and light", "red and medium and heavy" ...] Here's the caveat though This function must be able to take any number of sets of options I have a feeling that the proper way

问题 I am trying to make one statement to pull data from 3 related tables (as in they all share a common string index). I am having trouble preventing MySQL from returning the product of two of the tables, making the result set much larger than I want it. Each table has a different number of columns, and I would prefer to not use UNION anyway, because the data in each table is separate. Here is an example: Table X is the main table and has fields A B. Table Y has fields A C D. Table Z has fields A

问题 I am working on a project in which I have three box (as of now) and each box will have some color of balls So I am storing them in a Map of String and List of String as shown below. Map<String, List<String>> boxBallMap = new LinkedHashMap<String, List<String>>(); Data in the above map can be like this - {box1=[blue, red, orange]} {box2=[blue, red]} {box3=[blue, red, orange]} So possible combination of balls in the boxes can be - (POINT A) :: All boxes having same number of balls - {box1=[blue

问题 I have the following 2D array: String[M][] String[0] "1","2","3" String[1] "A", "B" . . . String[M-1] "!" All the possible combinations should be in store in a resulting array String[] combinations . So for example: combinations[0] == {"1A....!") combinations[1] == {"2A....!") combinations[2] == {"3A....!") combinations[3] == {"1B....!") Notice that that the arrays are of variable length. Order of the elements in the output String doesn't matter. I also don't care if there are duplicates. If

问题 I have a list and I need to output each subset of the list for example a b c d e would output to a b c d e ab ac ad ae abc abd abe bcd bce .... abcde I believe the correct term is combination no element should be duplicated on the same line I was going to attempt this with a series of loops but im not even sure wehre to start any suggestions? 回答1: This will generate the set you want, but in a different order (I sort by alphabet at the end, you'd want to sort by length as well). You'll end up

问题 Interview questions where I start with "this might be solved by generating all possible combinations for the array elements" are usually meant to let me find something better. Anyway I would like to add "I would definitely prefer another solution since this is O(X)".. the question is: what is the O(X) complexity of generating all combinations for a given set? I know that there are n! / (n-k)!k! combinations (binomial coefficients), but how to get the big-O notation from that? 回答1: First,

问题 I'm trying to implement a class that will generate all possible unordered n-tuples or combinations given a number of elements and the size of the combination. In other words, when calling this: NTupleUnordered unordered_tuple_generator(3, 5, print); unordered_tuple_generator.Start(); print() being a callback function set in the constructor. The output should be: {0,1,2} {0,1,3} {0,1,4} {0,2,3} {0,2,4} {0,3,4} {1,2,3} {1,2,4} {1,3,4} {2,3,4} This is what I have so far: class NTupleUnordered {

问题 I've recently written the following combinations and permutations functions for an F# project, but I'm quite aware they're far from optimised. /// Rotates a list by one place forward. let rotate lst = List.tail lst @ [List.head lst] /// Gets all rotations of a list. let getRotations lst = let rec getAll lst i = if i = 0 then [] else lst :: (getAll (rotate lst) (i - 1)) getAll lst (List.length lst) /// Gets all permutations (without repetition) of specified length from a list. let rec getPerms