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Power of Two⚓︎

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Description⚓︎

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

An integer n is a power of two, if there exists an integer x such that n == 2^x.

Example 1:

  • Input: n = 1
  • Output: true
  • Explanation: 2^0 = 1

Example 2:

  • Input: n = 16
  • Output: true
  • Explanation: 2^4 = 16

Example 3:

  • Input: n = 3
  • Output: false

Constraints:

  • -2^31 <= n <= 2^31 - 1

Solution⚓︎

Way 1⚓︎

See reference.

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class Solution {
public:
    bool isPowerOfTwo(int n) {
        if (n <= 0) return false;
        return (n & (n - 1)) == 0;
    }
};

Way 2⚓︎

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class Solution {
public:
    bool isPowerOfTwo(int n) {
        if (n <= 0) return false;
        return (1 << 30) % n == 0;
    }
};

Way 3⚓︎

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class Solution {
public:
    bool isPowerOfTwo(int n) {
        if (n <= 0) return false;
        return (n & -n) == n;
    }
};