Check if List values are consecutive

Question

List dansConList = new List();
dansConList[0] = 1;
dansConList[1] = 2;
dansConList[2] = 3;

List dansRandomList = new List

        

Answer 1

One-liner, only iterates until the first non-consecutive element:

bool isConsecutive = !myIntList.Select((i,j) => i-j).Distinct().Skip(1).Any();

Update: a couple examples of how this works:

Input is { 5, 6, 7, 8 }
Select yields { (5-0=)5, (6-1=)5, (7-2=)5, (8-3=)5 }
Distinct yields { 5, (5 not distinct, 5 not distinct, 5 not distinct) }
Skip yields { (5 skipped, nothing left) }
Any returns false

Input is { 1, 2, 6, 7 }
Select yields { (1-0=)1, (2-1=)1, (6-2=)4, (7-3=)4 } *
Distinct yields { 1, (1 not distinct,) 4, (4 not distinct) } *
Skip yields { (1 skipped,) 4 }
Any returns true

* The Select will not yield the second 4 and the Distinct will not check it, as the Any will stop after finding the first 4.

Answer 2

It is works for unique list only.

List<Int32> dansConList = new List<Int32>();
dansConList.Add(7);
dansConList.Add(8);
dansConList.Add(9);

bool b = (dansConList.Min() + dansConList.Max())*((decimal)dansConList.Count())/2.0m == dansConList.Sum();

Answer 3

var result = list
    .Zip(list.Skip(1), (l, r) => l + 1 == r)
    .All(t => t);

Answer 4

Extension method:

public static bool IsConsecutive(this IEnumerable<int> myList)
{
    return myList.SequenceEqual(Enumerable.Range(myList.First(), myList.Last()));
}

Useage:

bool isConsecutive = dansRandomList.IsConsecutive();

Answer 5

Here is an extension method that uses the Aggregate function.

public static bool IsConsecutive(this List<Int32> value){
    return value.OrderByDescending(c => c)
                .Select(c => c.ToString())
                .Aggregate((current, item) => 
                            (item.ToInt() - current.ToInt() == -1) ? item : ""
                            )
                .Any();
}

Usage:

var consecutive = new List<Int32>(){1,2,3,4}.IsConsecutive(); //true
var unorderedConsecutive = new List<Int32>(){1,4,3,2}.IsConsecutive(); //true
var notConsecutive = new List<Int32>(){1,5,3,4}.IsConsecutive(); //false

Answer 6

In order to check whether the series contain consecutive number or not you may use this

Sample

isRepeatable(121878999, 2);

Result = True

since 9 repeats two times , where upto is no of times in series

isRepeatable(37302293, 3)

Result = False

since no number repeat 3 times in series

static bool isRepeatable(int num1 ,int upto)
    {
        List<int> myNo = new List<int>();
        int previous =0;
        int series = 0;
        bool doesMatch = false;
        var intList = num1.ToString().Select(x => Convert.ToInt32(x.ToString())).ToList();
        for (int i = 0; i < intList.Count; i++)
        {
            if (myNo.Count==0)
            {
                myNo.Add(intList[i]);
                previous = intList[i];
                series += 1;
            }
            else
            {
                if (intList[i]==previous)
                {
                    series += 1;
                    if (series==upto)
                    {
                        doesMatch = true;
                        break;
                    }
                }
                else
                {
                    myNo = new List<int>();
                    previous = 0;
                    series = 0;
                }
            }
           
        }

        return doesMatch;

    }