Bitsets are a useful data structure in C++ that allows efficient manipulation of individual bits. In this blog post, we will explore how to count the number of unset bits in the odd and even positions of a bitset.

Background

A bitset is a fixed-size sequence of bits, where each bit can be either set (1) or unset (0). The std::bitset class in C++ provides a convenient way to store and manipulate such sequences.

Counting Unset Bits in Odd Positions

To count the number of unset bits in the odd positions of a bitset, we can use the bitwise AND operation to mask the even positions and then count the number of unset bits.

Here’s an example code snippet:

#include <iostream>
#include <bitset>

int countUnsetBitsOdd(const std::bitset<8>& bs) {
    std::bitset<8> oddMask("01010101");
    std::bitset<8> oddBits = bs & oddMask;
    return oddBits.count();
}

int main() {
    std::bitset<8> myBits("10101010");
    int unsetBitsCount = countUnsetBitsOdd(myBits);
    std::cout << "Number of unset bits in odd positions: " << unsetBitsCount << std::endl;
    return 0;
}

In the countUnsetBitsOdd function, we create a separate bitset oddMask with alternating 0s and 1s. We then use the bitwise AND operation (&) to apply the mask to the input bitset bs, which results in a bitset containing only the bits at odd positions. Finally, we use the count() function to count the number of unset bits in the odd positions.

Counting Unset Bits in Even Positions

Similarly, we can count the number of unset bits in the even positions by masking the odd positions.

Here’s an example code snippet:

#include <iostream>
#include <bitset>

int countUnsetBitsEven(const std::bitset<8>& bs) {
    std::bitset<8> evenMask("10101010");
    std::bitset<8> evenBits = bs & evenMask;
    return evenBits.count();
}

int main() {
    std::bitset<8> myBits("10101010");
    int unsetBitsCount = countUnsetBitsEven(myBits);
    std::cout << "Number of unset bits in even positions: " << unsetBitsCount << std::endl;
    return 0;
}

In the countUnsetBitsEven function, we create a separate bitset evenMask with alternating 1s and 0s. We then use the bitwise AND operation (&) to apply the mask to the input bitset bs, which results in a bitset containing only the bits at even positions. Again, we use the count() function to count the number of unset bits in the even positions.

Conclusion

In this blog post, we explored how to count the number of unset bits in the odd and even positions of a bitset in C++. We used bitwise operations and masking techniques to extract the desired positions and then counted the number of unset bits. Bitsets provide a convenient and efficient way to work with individual bits, making them a valuable tool in various applications. #programming #C++ #bitwise #bitset