Get all combinations of a list, grouped by name
I have the following TestParam list ... This is a parameter list that is used to determine how the request will be executed. In the following case, the expected result must be performed against all combinations of different parameters. Hence a list of lists with CustomerId 33 along with every product ID available in the list ...
List<TestParam> testList = new List<TestParam>();
testList.Add(new TestParam() { Name = "CustomerId", Value = "33" });
testList.Add(new TestParam() { Name = "ProductId", Value = "1" });
testList.Add(new TestParam() { Name = "ProductId", Value = "2" });
testList.Add(new TestParam() { Name = "ProductId", Value = "3" });
testList.Add(new TestParam() { Name = "ProductId", Value = "4" });
testList.Add(new TestParam() { Name = "ProductId", Value = "5" });
testList.Add(new TestParam() { Name = "ProductId", Value = "6" });
testList.Add(new TestParam() { Name = "ProductId", Value = "7" });
testList.Add(new TestParam() { Name = "ProductId", Value = "8" });
TestParam is a normal encapsulated parameter class with a name and a value ...
public class TestParam
{
public string Name { get; set; }
public string Value { get; set; }
}
The end result will be a list of lists with CustomerId 33, with all other products. The same result would be obtained if I had different names and values in the TestParam list (above example).
The following code ends with multiple lists depending on the combinations of the list above ...
// First get a list of distinct unique param collections...
List<string> distinctParameterNames = new List<string>();
testList.GroupBy(x => x.Name).ForEach(paramName => {
distinctParameterNames.Add(paramName.Key);
});
// Get counts
List<int> combinationList = new List<int>();
foreach (var x in distinctParameterNames) {
combinationList.Add(testList.Where(y=>y.Name == x).Count());
}
// Will contain 2 lists, one having all combinations of parameters named CustomerId, and another with ProductId combinations...
List<List<TestParam>> parameterList = new List<List<TestParam>>();
foreach (var x in distinctParameterNames) {
// Loop
List<TestParam> parameter = new List<TestParam>();
testList.Where(paramName => paramName.Name == x).ForEach(y =>
{
parameter.Add(new TestParam() { Name = y.Name, Value = y.Value });
});
parameterList.Add(parameter);
}
This will be the intersection between the list, and the end result will be a list of lists, and each list will have the following combinations ... So the launch will return (in this case):
- Customer 33, Product ID 1
- Customer 33, Product ID 2
- Customer 33, Product ID 3
- Customer 33, Product ID 4
- Customer 33, Product ID 5
- Customer 33, Product ID 6
- Customer 33, Product ID 7
- Customer 33, Product ID 8
What would be the most efficient and general way to do this?
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The following is the solution I was looking for ...
public static List<List<T>> AllCombinationsOf<T>(params List<T>[] sets)
{
// need array bounds checking etc for production
var combinations = new List<List<T>>();
// prime the data
foreach (var value in sets[0])
combinations.Add(new List<T> { value });
foreach (var set in sets.Skip(1))
combinations = AddExtraSet(combinations, set);
return combinations;
}
private static List<List<T>> AddExtraSet<T>
(List<List<T>> combinations, List<T> set)
{
var newCombinations = from value in set
from combination in combinations
select new List<T>(combination) { value };
return newCombinations.ToList();
}
Usage (continues with my code snippet of the question itself):
var intersection = AllCombinationsOf(parameterList.ToArray());
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first select the entire list of clients
var customers = from a in testlist where a.name='customerid'
select a;
var products = from a in testlist where a.name='productid'
select a;
then loop customers
for(var c in customers)
{
loop products
for(var p in products)
{
var customerproducts = new CustomerProducts{
Customer = c.Name +' ' + c.Value
Product = p.Name + ' ' + p.value
};
then add it into a list
}
}
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The list must be grouped by Name
, then it can be combined several times depending on the number of groups:
var groups = testList.GroupBy(_ => _.Name);
IEnumerable<IEnumerable<TestParam>> result = null;
foreach (var g in groups)
{
var current = g.Select(_ => new[] { _ });
if (result == null)
{
result = current;
continue;
}
result = result.Join(current, _ => true, _ => true, (actual, c) => actual.Concat(c));
}
// check result
foreach (var i in result)
{
Console.WriteLine(string.Join(", ", i.Select(_ => string.Format("{0}-{1}", _.Name, _.Value))));
}
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