Data Structures | Array | Question 2

Which of the following operations can be performed using bitwise operators in C to check if a number is a power of 2?

(A)

AND

(B)

OR

(C)

XOR

(D)

Shift

Answer: (A)

Explanation:

To check if a number is a power of 2 using bitwise operators in C, we can perform a bitwise AND operation between the given number and its one less value. If the result of this operation is zero, then the number is a power of 2.

For example, let’s say we want to check if the number x is a power of 2. We can do this as follows:

C++

if ((x & (x-1)) == 0) {
   // x is a power of 2
} else {
   // x is not a power of 2
}

Here, the & operator performs a bitwise AND operation, and the (x-1) term flips all the bits after the rightmost set bit in x. If x is already a power of 2, then x-1 will have all the bits flipped except for the rightmost set bit, which will remain unchanged. Therefore, the bitwise AND operation will yield zero. On the other hand, if x is not a power of 2, then x-1 will have at least two set bits that are adjacent, and the bitwise AND operation will yield a non-zero value.

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