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Generalized solution to creating k-sized sub/supersets from a given set


Reporting duplicate entry for a given set of dataLet's play some Swift PokerFrom scratch pub sub definition and implementationPoker app in C#Finding permutation from given lexicographical rankFind the nearest point of a given set of pointsFaster way to loop through array of points and find if within polygonsCreating a array of custom objects from JSON, sent using PHP from a MySQL databaseCounting contiguous subarrays with a negative sumIncrease performance creating Mandelbrot set in python






.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;








0












$begingroup$


In this code for a Set Game, using nested for-loops seems inevitable. But suppose there were more properties to provide for the Card initializer, the pyramid of nested loops would grow even bigger.



A possible solution could be to generate all the possible k-sized sub/supersets from the initial set, and then loop through them:



func combinations<C: Collection>(sized k: Int, from collection: C) -> [[C.Element]] 
var result: [[C.Element]] = [[]]
var lastCount = 1
while result[result.count - 1].count < k
for i in result.indices.suffix(lastCount)
for element in collection
result.append(result[i] + [element])


lastCount *= collection.count

return Array(result.suffix(lastCount))



A deck of cards would be created like so:



struct Card 
let number: Int
let symbol: Int
let color: Int
let shading: Int


var deck: [Card] = combinations(sized: 4, from: 1..<3)
.map Card(number : $0[0],
symbol : $0[1],
color : $0[2],
shading : $0[3])


The advantage of this approach is that it could be used to concoct subsets as well as supersets :



for comb in combinations(sized: 5, from: ["a", "b", "c"]) 
print(comb.joined()) //"aaaaa", "aaaab", ... , "ccccc"


//Or if you're feeling artsy
combinations(sized: 2, from: [UIColor.red, UIColor.green, UIColor.blue])


The one limitation is that it quickly goes slow for higher k or collection.count since this is an O(nk) algorithm I believe (n being the collection count). Is there a better way?



Feedback on all aspects of the code is welcome, such as (but not limited to):



  • Efficiency,

  • Readability,

  • Naming.









share|improve this question











$endgroup$


















    0












    $begingroup$


    In this code for a Set Game, using nested for-loops seems inevitable. But suppose there were more properties to provide for the Card initializer, the pyramid of nested loops would grow even bigger.



    A possible solution could be to generate all the possible k-sized sub/supersets from the initial set, and then loop through them:



    func combinations<C: Collection>(sized k: Int, from collection: C) -> [[C.Element]] 
    var result: [[C.Element]] = [[]]
    var lastCount = 1
    while result[result.count - 1].count < k
    for i in result.indices.suffix(lastCount)
    for element in collection
    result.append(result[i] + [element])


    lastCount *= collection.count

    return Array(result.suffix(lastCount))



    A deck of cards would be created like so:



    struct Card 
    let number: Int
    let symbol: Int
    let color: Int
    let shading: Int


    var deck: [Card] = combinations(sized: 4, from: 1..<3)
    .map Card(number : $0[0],
    symbol : $0[1],
    color : $0[2],
    shading : $0[3])


    The advantage of this approach is that it could be used to concoct subsets as well as supersets :



    for comb in combinations(sized: 5, from: ["a", "b", "c"]) 
    print(comb.joined()) //"aaaaa", "aaaab", ... , "ccccc"


    //Or if you're feeling artsy
    combinations(sized: 2, from: [UIColor.red, UIColor.green, UIColor.blue])


    The one limitation is that it quickly goes slow for higher k or collection.count since this is an O(nk) algorithm I believe (n being the collection count). Is there a better way?



    Feedback on all aspects of the code is welcome, such as (but not limited to):



    • Efficiency,

    • Readability,

    • Naming.









    share|improve this question











    $endgroup$














      0












      0








      0





      $begingroup$


      In this code for a Set Game, using nested for-loops seems inevitable. But suppose there were more properties to provide for the Card initializer, the pyramid of nested loops would grow even bigger.



      A possible solution could be to generate all the possible k-sized sub/supersets from the initial set, and then loop through them:



      func combinations<C: Collection>(sized k: Int, from collection: C) -> [[C.Element]] 
      var result: [[C.Element]] = [[]]
      var lastCount = 1
      while result[result.count - 1].count < k
      for i in result.indices.suffix(lastCount)
      for element in collection
      result.append(result[i] + [element])


      lastCount *= collection.count

      return Array(result.suffix(lastCount))



      A deck of cards would be created like so:



      struct Card 
      let number: Int
      let symbol: Int
      let color: Int
      let shading: Int


      var deck: [Card] = combinations(sized: 4, from: 1..<3)
      .map Card(number : $0[0],
      symbol : $0[1],
      color : $0[2],
      shading : $0[3])


      The advantage of this approach is that it could be used to concoct subsets as well as supersets :



      for comb in combinations(sized: 5, from: ["a", "b", "c"]) 
      print(comb.joined()) //"aaaaa", "aaaab", ... , "ccccc"


      //Or if you're feeling artsy
      combinations(sized: 2, from: [UIColor.red, UIColor.green, UIColor.blue])


      The one limitation is that it quickly goes slow for higher k or collection.count since this is an O(nk) algorithm I believe (n being the collection count). Is there a better way?



      Feedback on all aspects of the code is welcome, such as (but not limited to):



      • Efficiency,

      • Readability,

      • Naming.









      share|improve this question











      $endgroup$




      In this code for a Set Game, using nested for-loops seems inevitable. But suppose there were more properties to provide for the Card initializer, the pyramid of nested loops would grow even bigger.



      A possible solution could be to generate all the possible k-sized sub/supersets from the initial set, and then loop through them:



      func combinations<C: Collection>(sized k: Int, from collection: C) -> [[C.Element]] 
      var result: [[C.Element]] = [[]]
      var lastCount = 1
      while result[result.count - 1].count < k
      for i in result.indices.suffix(lastCount)
      for element in collection
      result.append(result[i] + [element])


      lastCount *= collection.count

      return Array(result.suffix(lastCount))



      A deck of cards would be created like so:



      struct Card 
      let number: Int
      let symbol: Int
      let color: Int
      let shading: Int


      var deck: [Card] = combinations(sized: 4, from: 1..<3)
      .map Card(number : $0[0],
      symbol : $0[1],
      color : $0[2],
      shading : $0[3])


      The advantage of this approach is that it could be used to concoct subsets as well as supersets :



      for comb in combinations(sized: 5, from: ["a", "b", "c"]) 
      print(comb.joined()) //"aaaaa", "aaaab", ... , "ccccc"


      //Or if you're feeling artsy
      combinations(sized: 2, from: [UIColor.red, UIColor.green, UIColor.blue])


      The one limitation is that it quickly goes slow for higher k or collection.count since this is an O(nk) algorithm I believe (n being the collection count). Is there a better way?



      Feedback on all aspects of the code is welcome, such as (but not limited to):



      • Efficiency,

      • Readability,

      • Naming.






      performance swift






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 20 mins ago







      ielyamani

















      asked 26 mins ago









      ielyamaniielyamani

      372213




      372213




















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