Today I have done Power of Four and leetcode's April LeetCoding Challenge with cpp.

Power of Four

Description

Given an integer n, return true if it is a power of four. Otherwise, return false.

An integer n is a power of four, if there exists an integer x such that n == 4x.

Example 1:

Input: n = 16
Output: true

Example 2:

Input: n = 5
Output: false

Example 3:

Input: n = 1
Output: true

Constraints:

• -231 <= n <= 231 - 1

Solution

class Solution {
public:
  bool isPowerOfFour(int n) {
    if(n < 1) return false;
    double p = log(n) / log(4);
    double diff = abs(p - floor(p));
    return diff < numeric_limits<double>::epsilon();  
  }
};

April LeetCoding challenge 30

Description

Find First and Last Position of Element in Sorted Array 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

class Solution {
public:
  vector<int> powerfulIntegers(int x, int y, int bound) {
    if(x == 1 && y == 1) {
      if(bound >= 2) return {2};
      return {};
    }
    if(x == 1 || y == 1) {
      int rest = x == 1 ? y : x;
      int cur = 1;
      vector<int> answer;
      while(cur + 1 <= bound) {
        answer.push_back(cur + 1);
        cur *= rest;
      }
      return answer;
    }
    unordered_set<int> answer;
    for(int i = 1; i + 1 <= bound; i *= x) {
      for(int j = 1; j + i <= bound; j *= y) {
        answer.insert(i + j);
      }
    }
    return vector<int>(answer.begin(), answer.end()); 
  }
};

// 102 / 102 test cases passed.
// Status: Accepted
// Runtime: 0 ms
// Memory Usage: 6.6 MB