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

// 1 | 2 | 3 | 4 | _
// _ | 1 | 2 | 3 | 4
//   | 1 | 1 | 1 |    => must be 1 (or 2 for even/odd consecutive integers)

var numbers = new List() { 1, 2, 3, 4, 5 };
const step = 1; // change to 2 for even and odd consecutive integers

var isConsecutive = numbers.Skip(1)
   .Zip(numbers.SkipLast(1))
   .Select(n => {
       var diff = n.First - n.Second;
       return (IsValid: diff == step, diff);
   })
   .Where(diff => diff.IsValid)
   .Distinct()
   .Count() == 1;

Or we could write that a bit shorter but less readable:

var isConsecutive = numbers.Skip(1)
   .Zip(numbers.SkipLast(1), (l, r) => (IsValid: (l-r == step), l-r))
   .Where(diff => diff.IsValid)
   .Distinct()
   .Count() == 1;