## 1. Brute Force ::tabs-start ```python class Solution: def isPowerOfTwo(self, n: int) -> bool: if n <= 0: return False x = 1 while x < n: x *= 2 return x == n ``` ```java public class Solution { public boolean isPowerOfTwo(int n) { if (n <= 0) return false; long x = 1; while (x < n) { x *= 2; } return x == n; } } ``` ```cpp class Solution { public: bool isPowerOfTwo(int n) { if (n <= 0) return false; long long x = 1; while (x < n) { x *= 2; } return x == n; } }; ``` ```javascript class Solution { /** * @param {number} n * @return {boolean} */ isPowerOfTwo(n) { if (n <= 0) return false; let x = 1; while (x < n) { x *= 2; } return x === n; } } ``` ```csharp public class Solution { public bool IsPowerOfTwo(int n) { if (n <= 0) { return false; } int x = 1; while (x < n) { x *= 2; } return x == n; } } ``` ::tabs-end ### Time & Space Complexity - Time complexity: $O(\log n)$ - Space complexity: $O(1)$ --- ## 2. Recursion ::tabs-start ```python class Solution: def isPowerOfTwo(self, n: int) -> bool: if n == 1: return True if n <= 0 or n % 2 == 1: return False return self.isPowerOfTwo(n // 2) ``` ```java public class Solution { public boolean isPowerOfTwo(int n) { if (n == 1) { return true; } if (n <= 0 || n % 2 == 1) { return false; } return isPowerOfTwo(n / 2); } } ``` ```cpp class Solution { public: bool isPowerOfTwo(int n) { if (n == 1) { return true; } if (n <= 0 || n % 2 == 1) { return false; } return isPowerOfTwo(n / 2); } }; ``` ```javascript class Solution { /** * @param {number} n * @return {boolean} */ isPowerOfTwo(n) { if (n === 1) { return true; } if (n <= 0 || n % 2 === 1) { return false; } return this.isPowerOfTwo(Math.floor(n / 2)); } } ``` ```csharp public class Solution { public bool IsPowerOfTwo(int n) { if (n == 1) { return true; } if (n <= 0 || n % 2 == 1) { return false; } return IsPowerOfTwo(n / 2); } } ``` ::tabs-end ### Time & Space Complexity - Time complexity: $O(\log n)$ - Space complexity: $O(\log n)$ for recursion stack. --- ## 3. Iteration ::tabs-start ```python class Solution: def isPowerOfTwo(self, n: int) -> bool: if n <= 0: return False while n % 2 == 0: n >>= 1 return n == 1 ``` ```java public class Solution { public boolean isPowerOfTwo(int n) { if (n <= 0) return false; while (n % 2 == 0) { n >>= 1; } return n == 1; } } ``` ```cpp class Solution { public: bool isPowerOfTwo(int n) { if (n <= 0) return false; while (n % 2 == 0) { n >>= 1; } return n == 1; } }; ``` ```javascript class Solution { /** * @param {number} n * @return {boolean} */ isPowerOfTwo(n) { if (n <= 0) return 0; while (n % 2 === 0) { n >>= 1; } return n === 1; } } ``` ```csharp public class Solution { public bool IsPowerOfTwo(int n) { if (n <= 0) { return false; } while (n % 2 == 0) { n >>= 1; } return n == 1; } } ``` ::tabs-end ### Time & Space Complexity - Time complexity: $O(\log n)$ - Space complexity: $O(1)$ --- ## 4. Bit Manipulation - I ::tabs-start ```python class Solution: def isPowerOfTwo(self, n: int) -> bool: return n > 0 and (n & (-n)) == n ``` ```java public class Solution { public boolean isPowerOfTwo(int n) { return n > 0 && (n & (-n)) == n; } } ``` ```cpp class Solution { public: bool isPowerOfTwo(int n) { return n > 0 && (n & (-n)) == n; } }; ``` ```javascript class Solution { /** * @param {number} n * @return {boolean} */ isPowerOfTwo(n) { return n > 0 && (n & -n) === n; } } ``` ```csharp public class Solution { public bool IsPowerOfTwo(int n) { return n > 0 && (n & -n) == n; } } ``` ::tabs-end ### Time & Space Complexity - Time complexity: $O(1)$ - Space complexity: $O(1)$ --- ## 5. Bit Manipulation - II ::tabs-start ```python class Solution: def isPowerOfTwo(self, n: int) -> bool: return n > 0 and (n & (n - 1)) == 0 ``` ```java public class Solution { public boolean isPowerOfTwo(int n) { return n > 0 && (n & (n - 1)) == 0; } } ``` ```cpp class Solution { public: bool isPowerOfTwo(int n) { return n > 0 && (n & (n - 1)) == 0; } }; ``` ```javascript class Solution { /** * @param {number} n * @return {boolean} */ isPowerOfTwo(n) { return n > 0 && (n & (n - 1)) === 0; } } ``` ```csharp public class Solution { public bool IsPowerOfTwo(int n) { return n > 0 && (n & (n - 1)) == 0; } } ``` ::tabs-end ### Time & Space Complexity - Time complexity: $O(1)$ - Space complexity: $O(1)$ --- ## 6. Math ::tabs-start ```python class Solution: def isPowerOfTwo(self, n: int) -> bool: return n > 0 and ((1 << 30) % n) == 0 ``` ```java public class Solution { public boolean isPowerOfTwo(int n) { return n > 0 && ((1 << 30) % n) == 0; } } ``` ```cpp class Solution { public: bool isPowerOfTwo(int n) { return n > 0 && ((1 << 30) % n) == 0; } }; ``` ```javascript class Solution { /** * @param {number} n * @return {boolean} */ isPowerOfTwo(n) { return n > 0 && (1 << 30) % n === 0; } } ``` ```csharp public class Solution { public bool IsPowerOfTwo(int n) { return n > 0 && ((1 << 30) % n) == 0; } } ``` ::tabs-end ### Time & Space Complexity - Time complexity: $O(1)$ - Space complexity: $O(1)$

Power of Two