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C++ Bitset

The C++ std::bitset is a standard library class provided by the <bitset> header that represents a fixed-size sequence of bits. It is a container that stores a sequence of binary values (0s and 1s) and provides various operations for manipulating and inspecting these bits. Here’s an overview of how to use std::bitset:

Declaration and Initialization:

You can declare and initialize a std::bitset with a specified size during declaration or later. For example:

C++
#include <bitset>
#include <iostream>

int main() {
    // Declare and initialize a bitset of size 8 with all bits set to 0.
    std::bitset<8> bits1;

    // Initialize a bitset with a binary string.
    std::bitset<8> bits2("10101010");

    // Initialize a bitset with an integer value.
    std::bitset<8> bits3(170);

    std::cout << "bits1: " << bits1 << std::endl;
    std::cout << "bits2: " << bits2 << std::endl;
    std::cout << "bits3: " << bits3 << std::endl;

    return 0;
}

Bit Manipulation:

std::bitset provides various methods for manipulating individual bits or sets of bits, including:

  • set(): Sets a specific bit to 1.
  • reset(): Resets (sets to 0) a specific bit.
  • flip(): Toggles (flips) the value of a specific bit.
  • test(): Tests the value of a specific bit.
C++
std::bitset<8> bits(42);
bits.set(2); // Set the 3rd bit to 1
bits.reset(5); // Reset the 6th bit to 0
bits.flip(0); // Toggle the 1st bit
bool bitValue = bits.test(3); // Test the 4th bit

Bitwise Operations:

You can perform bitwise operations on std::bitset objects, including AND (&), OR (|), XOR (^), and NOT (~).

C++
std::bitset<8> bits1("11001100");
std::bitset<8> bits2("10101010");

std::bitset<8> resultAND = bits1 & bits2;
std::bitset<8> resultOR = bits1 | bits2;
std::bitset<8> resultXOR = bits1 ^ bits2;
std::bitset<8> resultNOT = ~bits1;

Conversion:

You can convert a std::bitset to an integer using the to_ulong() or to_ullong() functions. These functions return the decimal equivalent of the binary representation stored in the bitset.

C++
std::bitset<8> bits("10101010");
unsigned long decimalValue = bits.to_ulong();

Size and Count:

You can get the size (number of bits) of a std::bitset using the size() function, and you can count the number of set bits (1s) using the count() function.

C++
std::bitset<8> bits("10101010");
size_t size = bits.size(); // Returns 8
size_t countSetBits = bits.count(); // Returns 4

std::bitset is useful when you need to work with a fixed-size sequence of bits and perform bit-level operations efficiently.

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