LeetCode //C - 342. Power of Four

342. Power of Four

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 = = 4 x n == 4^x n==4x.

Example 1:

Input: n = 16
Output: true

Example 2:

Input: n = 5
Output: false

Example 3:

Input: n = 1
Output: true

Constraints:

• − 2 31 < = n < = 2 31 − 1 -2^{31} <= n <= 2^{31} - 1 −231<=n<=231−1

From: LeetCode

Link: 342. Power of Four

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Solution:

Ideas:

• n > 0: Ensures the number is positive.
• (n & (n - 1)) == 0: This checks if n is a power of two.
• (n & 0x55555555) != 0: This checks that the single bit set in n is in an odd position, confirming that n is a power of four.

Code:

bool isPowerOfFour(int n) {
    // Check if n is positive and a power of two
    if (n > 0 && (n & (n - 1)) == 0) {
        // Check if the single set bit is in an odd position
        return (n & 0x55555555) != 0;
    }
    return false;
}