LeetCode-in-Java

970. Powerful Integers

Medium

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

Solution

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;

public class Solution {
    public List<Integer> powerfulIntegers(int x, int y, int bound) {
        int iBound = (x == 1 ? 1 : (int) (Math.log10(bound) / Math.log10(x)));
        int jBound = (y == 1 ? 1 : (int) (Math.log10(bound) / Math.log10(y)));
        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i <= iBound; i++) {
            for (int j = 0; j <= jBound; j++) {
                int number = (int) (Math.pow(x, i) + Math.pow(y, j));
                if (number <= bound) {
                    set.add(number);
                }
            }
        }
        return new ArrayList<>(set);
    }
}

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