I want to have all combination of elements in a list for a result like this:
List: {1,2,3}
1
2
3
1,2
1,3
2,3
My problem is that I have 180 elements, and I want to have all combinations up to 5 elements. With my tests with 4 elements, it took a long time (2 minutes) but all went well. But with 5 elements, I get a run out of memory exception.
My code presently is this:
public IEnumerable<IEnumerable<Rondin>> getPossibilites(List<Rondin> rondins)
{
var combin5 = rondins.Combinations(5);
var combin4 = rondins.Combinations(4);
var combin3 = rondins.Combinations(3);
var combin2 = rondins.Combinations(2);
var combin1 = rondins.Combinations(1);
return combin5.Concat(combin4).Concat(combin3).Concat(combin2).Concat(combin1).ToList();
}
With the fonction: (taken from this question: Algorithm to return all combinations of k elements from n)
public static IEnumerable<IEnumerable<T>> Combinations<T>(this IEnumerable<T> elements, int k)
{
return k == 0 ? new[] { new T[0] } :
elements.SelectMany((e, i) =>
elements.Skip(i + 1).Combinations(k - 1).Select(c => (new[] { e }).Concat(c)));
}
I need to search in the list for a combination where each element added up is near (with a certain precision) to a value, this for each element in an other list. There is all my code for this part:
var possibilites = getPossibilites(opt.rondins);
possibilites = possibilites.Where(p => p.Sum(r => r.longueur + traitScie) < 144);
foreach(BilleOptimisee b in opt.billesOptimisees)
{
var proches = possibilites.Where(p => p.Sum(r => (r.longueur + traitScie)) < b.chute && Math.Abs(b.chute - p.Sum(r => r.longueur)) - (p.Count() * 0.22) < 0.01).OrderByDescending(p => p.Sum(r => r.longueur)).ElementAt(0);
if(proches != null)
{
foreach (Rondin r in proches)
{
opt.rondins.Remove(r);
b.rondins.Add(r);
possibilites = possibilites.Where(p => !p.Contains(r));
}
}
}
With the code I have, how can I limit the memory taken by my list ? Or is there a better solution to search in a very big set of combinations ?
Please, if my question is not good, tell me why and I will do my best to learn and ask better questions next time ;)