What's a good, generic algorithm for collapsing a set of potentially-overlapping ranges?

Question

I have a method that gets a number of objects of this class

class Range
{
    public T Start;
    public T End;
}

In my case

Answer 1

This could probably be optimized...

using System.Collections.Generic;
using System.Linq;
using System;
static class Range
{
    public static Range Create(T start, T end)
    {
        return new Range(start, end);
    }
    public static IEnumerable> Normalize(
        this IEnumerable> ranges)
    {
        return Normalize(ranges, null);
    }
    public static IEnumerable> Normalize(
        this IEnumerable> ranges, IComparer comparer)
    {
        var list = ranges.ToList();
        if (comparer == null) comparer = Comparer.Default;
        for (int i = list.Count - 1; i >= 0; i--)
        {
            var item = list[i];

            for (int j = 0; j < i; j++)
            {
                Range? newValue = TryMerge(comparer, item, list[j]);

                // did we find a useful transformation?
                if (newValue != null)
                {
                    list[j] = newValue.GetValueOrDefault();
                    list.RemoveAt(i);
                    break;
                }
            }
        }
        list.Sort((x, y) =>
        {
            int t = comparer.Compare(x.Start, y.Start);
            if (t == 0) t = comparer.Compare(x.End, y.End);
            return t;
        });
        return list.AsEnumerable();
    }

    private static Range? TryMerge(IComparer comparer, Range item, Range other)
    {
        if (comparer.Compare(other.End, item.Start) == 0)
        { // adjacent ranges
            return new Range(other.Start, item.End);
        }
        if (comparer.Compare(item.End, other.Start) == 0)
        { // adjacent ranges
            return new Range(item.Start, other.End);
        }
        if (comparer.Compare(item.Start, other.Start) <= 0
            && comparer.Compare(item.End, other.End) >= 0)
        { // item fully swalls other
            return item;
        }
        if (comparer.Compare(other.Start, item.Start) <= 0
            && comparer.Compare(other.End, item.End) >= 0)
        { // other fully swallows item
            return other;
        }
        if (comparer.Compare(item.Start, other.Start) <= 0
            && comparer.Compare(item.End, other.Start) >= 0
            && comparer.Compare(item.End, other.End) <= 0)
        { // partial overlap
            return new Range(item.Start, other.End);
        }
        if (comparer.Compare(other.Start, item.Start) <= 0
             && comparer.Compare(other.End, item.Start) >= 0
            && comparer.Compare(other.End, item.End) <= 0)
        { // partial overlap
            return new Range(other.Start, item.End);
        }
        return null;
    }
}
public struct Range
{
    private readonly T start, end;
    public T Start { get { return start; } }
    public T End { get { return end; } }
    public Range(T start, T end)
    {
        this.start = start;
        this.end = end;
    }
    public override string ToString()
    {
        return start + " to " + end;
    }
}

static class Program
{
    static void Main()
    {
        var data = new[] 
        {
            Range.Create(1,5), Range.Create(3,9),
            Range.Create(11,15), Range.Create(12,14),
            Range.Create(13,20)
        };
        var result = data.Normalize();
        foreach (var item in result)
        {
            Console.WriteLine(item);
        }
    }
}