Leetcode 56 - Merge Intervals - pass leetcode online judge

Leetcode56_MergeIntervals.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MergeIntervals
{
    class Program
    {
        /**
         * Definition for an interval.
         */
         public class Interval {
            public int start;
            public int end;
            public Interval() { start = 0; end = 0; }
            public Interval(int s, int e) { start = s; end = e; }
         }                 

        static void Main(string[] args)
        {
            RunSampleTestcase1();
            RunSampleTestcase2(); 
        }

        /*
         * Test case: 
         * help to test intervals should be sorted first before merging. 
         * [1,4], [0,4] should not be [1,4]
         */
        public static void RunSampleTestcase1()
        {
            IList<Interval> intervals = new List<Interval>();
            intervals.Add(new Interval(1, 4));
            intervals.Add(new Interval(0, 4));

            IList<Interval> nonoverlapped = Merge(intervals); 
            Debug.Assert(nonoverlapped[0].start == 0 && nonoverlapped[0].end == 4); 
        }

        /*
         * Test case: 
         * help to test that edge case is handled properly . 
         * [1,4] should be [1,4], not []
         * In other words, there is one interval in the input, the result should be itself. 
         * For loop 
         */
        public static void RunSampleTestcase2()
        {
            IList<Interval> intervals = new List<Interval>();
            intervals.Add(new Interval(1, 4));            

            IList<Interval> nonoverlapped = Merge(intervals);
            Debug.Assert(nonoverlapped.Count == 1); 
        }

        /*
         * Merge all overlapping intervals
         * Output: all intervals are non-overlapped. 
         * 
         * Use LINQ to sort the intervals - 
         * http://stackoverflow.com/questions/15486/sorting-an-ilist-in-c-sharp
         */
        public static IList<Interval> Merge(IList<Interval> intervals)
        {
            IList<Interval> nonOverlapped = new List<Interval>(); 
            if(intervals == null || intervals.Count == 0)
            {
                return nonOverlapped; 
            }

            IEnumerable<Interval> sortedEnumerable = intervals.OrderBy(f => f.start);
            IList<Interval> sortedIntervals = sortedEnumerable.ToList();

            Interval previous = sortedIntervals[0];
            for (int i = 1; i < sortedIntervals.Count; i++)
            {
                Interval current = sortedIntervals[i]; 

                if(previous.end < current.start)
                {
                    nonOverlapped.Add(previous);
                    previous = current;
                    continue;
                }

                previous = new Interval(previous.start, Math.Max(previous.end, current.end)); 
            }

            // edge case 
            nonOverlapped.Add(previous); 

            return nonOverlapped; 
        }             
    }
}