黑科技--位集--bitset

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

<bitset>

std::bitset

template <size_t N> 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<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<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;
}

【结果如下】

1
1000
0
1
1
0
0
1
0
1
1000
1