30. Powerful Integers.cpp

/*
Powerful Integers
=================

Given three integers x, y, and bound, return a list of all the powerful integers that have a value less than or equal to bound.

An integer is powerful if it can be represented as xi + yj for some integers i >= 0 and j >= 0.

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 = 20 + 30
3 = 21 + 30
4 = 20 + 31
5 = 21 + 31
7 = 22 + 31
9 = 23 + 30
10 = 20 + 32

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

Constraints:
1 <= x, y <= 100
0 <= bound <= 106
*/

class Solution
{
public:
  vector<int> powerfulIntegers(int x, int y, int bound)
  {
    unordered_set<int> s;
    for (int i = 1; i <= bound; i = i * x)
    {
      for (int j = 1; i + j <= bound; j = j * y)
      {
        s.insert(i + j);
        if (y == 1)
          break;
      }
      if (x == 1)
        break;
    }
    return vector<int>(s.begin(), s.end());
  }
};