Overlapping Ranges Check for Overlapping

Question

I have a list of ranges and I would like to find out if they overlap.

I have the following code. Which does not seem to be working. Is there an easier way to do this or a way that works :)

Thanks in advance for any advice.

   public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private IList<Range> rangeList;

    private void Form1_Load(object sender, EventArgs e)
    {
        rangeList.Add(new Range{FromNumber = 0, ToNumber = 100});
        rangeList.Add(new Range { FromNumber = 101, ToNumber = 200 });

        // this range should over lap and throw an exception 
        rangeList.Add(new Range { FromNumber = 199, ToNumber = 300 });

    }

    private bool RangesOverlap()
    {
        var bigList = new List<List<int>>();

        foreach (var range in this.rangeList)
        {
            bigList.Add(new List<int> { range.FromNumber , range.ToNumber });
        }

        IEnumerable<IEnumerable<int>> lists = bigList;

        return lists
         .Where(c => c != null && c.Any())
         .Aggregate(Enumerable.Intersect)
         .ToList().Count > 0;
    }
}


public class Range
{
    public int FromNumber { get; set; }
    public int ToNumber { get; set; }
}

Answer 1

First merge numbers and then check generated list is in sorted order:

rangeList
.OrderBy(p => p.FromNumber)
.Select(p => new[] { p.FromNumber, p.ToNumber })
.SelectMany(p => p)
.Aggregate((p, q) => q >= p ? q : int.MaxValue) == int.MaxValue

Answer 2

In the past I faced a challenge where I had to write a validating algorithm for ranges that are created by the user (integers or reals). I had to check 3 things:

1. Ranges are continuous
2. Ranges are not overlapping
3. LOW value must be always <= than HIGH

So I came up with the following PHP algorithm.

 //Let's hardcode an array of integers (it can be of reals as well):
 $range = array
 (
     array(1, 13),
     array(14, 20),
     array(21, 45),
     array(46, 50),
     array(51, 60)
 );

 //And the validation algorithm:
 $j = 0;
 $rows = sizeof($range);
 $step = 1;   // This indicates the step of the values.
              // 1 for integers, 0.1 or 0.01 for reals

 for ($x=0; $x<$rows; $x++)
     for ($y=0; $y<$rows; $y++) {
         if ( ($range[$x][0] <= $range[$y][0]) AND ($range[$y][0] <= $range[$x][1]) AND ($x != $y) ) {
             echo "Ranges intercepting";   // replace with error handling code
             break 3;
         }
         if ( $range[$x][0] > $range[$x][1] ) {
             echo "Not valid high & low";  // replace with error handling code
             break 3;
         }
         if ( $range[$x][0] - $range[$y][1] == $step ) {
             $j++;
         }
     }
 if ( $j != $rows - $step )
     echo "Not continuous";    // replace with error handling code

We iterate through the ranges and compare them in pairs. For each pair we:

1. find overlapping ranges and raise an error
2. find start & end points in reverse and raise an error

If none of the above occurs, we count the difference of end - start points. This number must be equals to the number of ranges minus the step (1, 0.1, 0.01, etc). Otherwise we raise an error.

Hope this helps!

Answer 3

You can fulfill your new requirement with a slight modification of RezaArabs answer:

rangeList
.Select(p => new[] { p.FromNumber, p.ToNumber })
.SelectMany(p => p.Distinct())
.Aggregate((p, q) => q >= p ? q : int.MaxValue) == int.MaxValue