C# Split time List into time ranges

Question

I am looking to extract ranges from an list of integers using linq:

for example I am looking to split the following list:

List<int> numberList = new List<int>() { 30, 60, 90, 120, 150, 180, 270, 300, 330 };  

into a list of integer ranges that will look like:

{ 30, 180 }
{ 270, 330 }

ie: where the next seq is greater than 30

another example :

List<int> numberList = new List<int>() { 30, 60, 120, 150, 270, 300, 330 };  

into a list of integer ranges that will look like:

{ 30, 60 }
{ 120, 150 }
{ 270, 330 }

I have tried with for loops to find the best way possible however I don't know where to start trying to use a linq query to do this.

Answer 1

You could write a method to handle the split:

IEnumerable<IList<int>> SplitValues(IList<int> input, int difference = 30)
{
    List<int> results = new List<int>();
    int last = input.First();
    foreach(var value in input)
    {
        if (value - last > difference)
        {
            yield return new[] {results.First(), results.Last()};
            results = new List<int>();
        }

        results.Add(value);
        last = value;
    }

    yield return new[] {results.First(), results.Last()};
}

This matches your specifications as described, returning:

{ 30, 60 }
{ 120, 150 }
{ 270, 330 }

Note that a single value within the collection without a range will be duplicated. For example, { 30, 120, 150 } will return:

{ 30, 30 }
{ 120, 150 }

Answer 2

You can do this in one linq statement:

var numberList = new List<int>() { 30, 60, 120, 150, 270, 300, 330 };
var section = 0;
var result = numberList
            .Select( (x, i) => new {value = x, section = (i == 0 ? 0 : ((x - numberList[i - 1]) > 30 ? ++section : section))})
            .GroupBy(x => x.section)
            .Select(x => x.Select(v => v.value).ToList()).ToList();