Check for missing number in sequence

Question

I have an List which contains 1,2,4,7,9 for example.

I have a range from 0 to 10.

Is there a way to determine what numbers are missin

Answer 1

this method here returns the number of missing elements ,sort the set , add all elements from range 0 to range max , then remove the original elements , then you will have the missing set

int makeArrayConsecutive(int[] statues) 
{

Array.Sort(statues);    
HashSet set = new HashSet();

for(int i = statues[0]; i< statues[statues.Length -1]; i++)
 {
  set.Add(i);
 }

for (int i = 0; i < statues.Length; i++)
{
 set.Remove(statues[i]);
}

var x = set.Count;    
return x;
// return set ; // use this if you need the actual elements + change the method return type        
}