1780

1780. Check if Number is a Sum of Powers of Three (Medium)

Given an integer n, return true if it is possible to represent n as the sum of distinct powers of three. Otherwise, return false.

An integer y is a power of three if there exists an integer x such that y == 3x.

 

Example 1:

Input: n = 12
Output: true
Explanation: 12 = 31 + 32

Example 2:

Input: n = 91
Output: true
Explanation: 91 = 30 + 32 + 34

Example 3:

Input: n = 21
Output: false

 

Constraints:

• 1 <= n <= 107

Companies:
Microsoft

Related Topics:
Math, Backtracking, Recursion

Similar Questions:

• Power of Three (Easy)

Solution 1.

// OJ: https://leetcode.com/problems/check-if-number-is-a-sum-of-powers-of-three/
// Author: github.com/lzl124631x
// Time: O(log_3^N)
// Space: O(1)
class Solution {
public:
    bool checkPowersOfThree(int n) {
        while (n % 3 == 0 || (n % 3 == 1 && n != 1)) {
            if (n % 3 == 1) n -= 1;
            n /= 3;
        }
        return n == 1;
    }
};