Difference between std::bitset and std::vector<bool> and an array of bool
Vector of bool and array of bool can also be implemented to store a sequence of boolean values like bitset but there are some differences between each implementation:
| Parameter | bitset | vector of bool | array of bool |
|---|---|---|---|
| Definition | A class template consisting of a sequence of bits stored such that each bit occupies 1 bit of memory. | A variation of vectors of C++ STL in which each element is of size 1 bit and is of type bool | A fixed size contiguous collection of bool data elements. |
| Size | Fixed Size. | Dynamic Size. | Fixed Size. |
| Memory | A single element occupies 1 bit of memory. | A single element occupies 1 bit of memory. | A single element occupies 1 byte of memory. |
| Speed | Same | Same | Faster |
C++ bitset and its application
A bitset is an array of bools but each boolean value is not stored in a separate byte instead, bitset optimizes the space such that each boolean value takes 1-bit space only, so space taken by bitset is less than that of an array of bool or vector of bool.
A limitation of the bitset is that size must be known at compile time i.e. size of the bitset is fixed.
std::bitset is the class template for bitset that is defined inside <bitset> header file so we need to include the header file before using bitset in our program.
Syntax:
bitset<size> variable_name(initialization);
We can initialize bitset in three ways :
1. Uninitialized: All the bits will be set to zero.
bitset<size> variable_name;
2. Initialization with decimal integer: Bitset will represent the given decimal number in binary form.
bitset<size> variable_name(DECIMAL_NUMBER);
3. Initialization with binary string: Bitset will represent the given binary string.
bitset<size> variable_name(string("BINARY_STRING"));
bitset<size> variable_name("BINARY_STRING");
Example:
// C++ program to demonstrate the bitset
#include <bitset>
#include <iostream>
using namespace std;
int main()
{
// declaring an uninitialized bitset object
bitset<8> uninitializedBitset;
// initialization with decimal number
bitset<8> decimalBitset(15);
// initialization with binary string
bitset<8> stringBitset(string("1111"));
cout << "Uninitialized bitset: " << uninitializedBitset
<< endl;
cout << "Initialized with decimal: " << decimalBitset
<< endl;
cout << "Initialized with string: " << stringBitset
<< endl;
return 0;
}
Output
Uninitialized bitset: 00000000 Initialized with decimal: 00001111 Initialized with string: 00001111
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