std::bitset
template <size_t N> class bitset;
Abtsetstores bits (elements with only two possible values: 0 or 1, true
or false
, ...). //位集用于存储0、1元素。
The class emulates an array of bool
elements, but optimized for space allocation: generally, each element occupies only one bit (which, on most systems, is eight times less than the smallest elemental type: char
). //这种类模拟了bool数组,但是单个元素占空间只有1bit。(!!好东西有木有!!)
Each bit position can be accessed individually: for example, for a given bitset named foo
, the expression foo[3]
accesses its fourth bit, just like a regular array accesses its elements. But because no elemental type is a single bit in most C++ environments, the individual elements are accessed as special references type (seebitset::reference). //每个位都能被独立访问。(!!好东西有木有!!)
Bitsets have the feature of being able to be constructed from and converted to both integer values and binary strings (see its constructor and membersto_ulong andto_string ). They can also be directly inserted and extracted from streams in binary format (see applicable operators). //这货还提供转化成其他类型的函数(!!好东西有木有!!)
Thesize of a bitset is fixed at compile-time (determined by its template parameter). For a class that also optimizes for space allocation and allows for dynamic resizing, see the bool
specialization ofvector (vector<bool>
).
Template parameters
- N
- Size of the bitset, in terms of number of bits. It is returned by member functionbitset::size.size_t is an unsigned integral type. //大小由位数决定,并且可以引用内置函数直接查询某一bitset的大小
Member types
- reference
- Reference-like type (public member class )
Member functions
- (constructor)
- Construct bitset (public member function )
- applicable operators
- Bitset operators (function )
Bit access
- operator[]
- Access bit (public member function ) //访问位集中的元素可以直接像访问数组一样完成
- count
- Count bits set (public member function ) //计数有多少位
- size
- Return size (public member function ) //返回空间大小
- test
- Return bit value (public member function ) //返回...这什么东西?
- any
- Test if any bit is set (public member function ) //返回位集中是否有元素1
- none
- Test if no bit is set (public member function ) //返回位集是否全空
- all
- Test if all bits are set (public member function ) //返回位集是否全满
Bit operations
- set
- Set bits (public member function ) //设置位
- reset
- Reset bits (public member function ) //清空位集
- flip
- Flip bits (public member function ) //位集元素置反
Bitset operations
- to_string
- Convert to string (public member function )
- to_ulong
- Convert to unsigned long integer (public member function )
- to_ullong
- Convert to unsigned long long (public member function )
Non-member function overloads
- applicable operators
- Bitset operators (function )
Non-member class specializations
- hash<bitset>
- Hash for bitset (class template specialization )
【主要操作测试】
#include<iostream>
#include<cstdio>
#include<bitset> using namespace std; int main()
{
bitset<> a; a[]=; //直接赋值
cout << a.count() << endl; //计数1的个数
cout << a.size() << endl; //返回空间大小
cout << a.test() << endl;
cout << a.test() << endl; //判断第i位是否为1
cout << a.any() << endl; //是否非空
cout << a.none() << endl; //是否全空
cout << a.all() << endl; //是否全满 a.set(); //与赋值相同
cout << a[] << endl; //直接访问,与test相同 a.reset(); //清空
cout << a.count() << endl;
cout << a.none() << endl; a.flip(); //反置
cout << a.count() << endl;
cout << a.all() << endl;
}
【结果如下】