自从上次网赛发现这么个东西之后，深深地感受到了bitset的强大，0.0。

正常的bool占用1字节空间，bitset可以把这个缩到1bit，空间上8倍优化。正常用起来可能会跟位运算状态压缩类似，但是其中的每个位又能进行单独操作，所以确实相当方便。

下面是原版的文档：

class template

std::bitset

template class bitset;

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).

Template parameters

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

referenceReference-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 operatorsBitset operators (function )

Non-member class specializations

hash Hash for bitset (class template specialization )

主要操作测试

#include<iostream>
#include<cstdio>
#include<bitset>

using namespace std;

int main()
{
    bitset<1000> a;
    
    a[100]=1;    //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(1) << endl;
    cout << a.test(100) << 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(2);    //与赋值相同 
    cout << a[2] << 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;
}

输出结果如下：

Chenfan Blog

黑科技--位集--bitset