Powerful Integers

Simple problem: https://leetcode.com/problems/powerful-integers/description/

Given two non-negative integers x and y, an integer is powerful if it is equal to x^i + y^j for some integers i >= 0 and j >= 0.

Return a list of all powerful integers that have value less than or equal to bound.

You may return the answer in any order.  In your answer, each value should occur at most once.

Example 1:

Input: x = 2, y = 3, bound = 10
Output: [2,3,4,5,7,9,10]
Explanation: 
2 = 2^0 + 3^0
3 = 2^1 + 3^0
4 = 2^0 + 3^1
5 = 2^1 + 3^1
7 = 2^2 + 3^1
9 = 2^3 + 3^0
10 = 2^0 + 3^2

Example 2:

Input: x = 3, y = 5, bound = 15
Output: [2,4,6,8,10,14]

Note:

• 1 <= x <= 100
• 1 <= y <= 100
• 0 <= bound <= 10^6

Code will run in up to 10^6, which is fine. Do a sieves-style, avoid Math.Pow, hash-table the solution to avoid dupes, handle cases when the input is 1 (special), other than that, two nested loops ought to do it. Thanks, ACC.

public class Solution
{
 public IList PowerfulIntegers(int x, int y, int bound)
 {
  List retVal = new List();
  Hashtable seen = new Hashtable();

  int min = Math.Min(x, y);
  int max = Math.Max(x, y);

  for (int p1 = 1; p1 <= bound; p1 *= min)
  {
   for (int p2 = 1; p1 + p2 <= bound; p2 *= max)
   {
    if (!seen.ContainsKey(p1 + p2))
    {
     seen.Add(p1 + p2, true);
     retVal.Add(p1 + p2);
    }

    if (max == 1) break;
   }

   if (min == 1) break;
  }

  return retVal;
 }
}