Power of Three

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326.Power of Three

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

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

Example 1:

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Input: n = 27
Output: true
Explanation: 27 = 33

Example 2:

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Input: n = 0
Output: false
Explanation: There is no x where 3x = 0.

Example 3:

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Input: n = -1
Output: false
Explanation: There is no x where 3x = (-1).

时间复杂度：O(logn)

空间复杂度：O(1)

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class Solution {
public:
    bool isPowerOfThree(int n) {
        while (n && n % 3 == 0) {
            n /= 3;
        }
        return n == 1;
    }
};

最大约数法：

时间复杂度：O(1)

空间复杂度：O(1)

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class Solution {
public:
    bool isPowerOfThree(int n) {
        return n > 0 && 1162261467 % n == 0;
    }
};