aritmmetic triplets

Solution.cs

public class Solution {
  public int ArithmeticTriplets(int[] nums, int diff) {
    var set = new HashSet<string>();
    
    int i = 0;
    int n = nums.Length-1;
    int c = 0;
   
    while(i <= n-2)
    {
      int j = i + 1;
      
      while(j <= n)
      {
        if(nums[j]-nums[i] == diff)
        {
          int k = j + 1;
          while(k <= n)
          {
            if(nums[k]-nums[j] == diff)
            {
              if(set.Add($"{nums[i]}-{nums[j]}-{nums[k]}"))
              {
                c++;
              }
              break;
            }
            k++;
          }
          break;
        }
        j++;
      }
      i++;
    }
    
    return c;
  }
}