C++ STL之array

Array 容器的相关知识，array是一个顺序容器，和其他标准容器相比它的特点是容器的大小固定，顺序存储。

1：array的构造函数

array（）；

array（const array &right）；

2：array的成员变量

Type Definition

Description

array::const_iterator

The type of a constant iterator for the controlledsequence.

array::const_pointer

The type of a constant pointer to anelement.

array::const_reference

The type of a constant reference to anelement.

array::const_reverse_iterator

The type of a constant reverse iterator for thecontrolled sequence.

array::difference_type

The type of a signed distance between twoelements.

array::iterator

The type of an iterator for the controlledsequence.

array::pointer

The type of a pointer to an element.

array::reference

The type of a reference to an element.

array::reverse_iterator

The type of a reverse iterator for the controlledsequence.

array::size_type

The type of an unsigned distance between twoelements.

array::value_type

The type of an element.

3：array的关于迭代器的成员函数

Iterators

begin   Return iterator to beginning (public member function )

end             Return iterator to end (public member function )

rbegin  Return reverse iterator toreverse beginning (public member function )

rend           Return reverse iterator to reverse end (public member function )

cbegin  Return const_iterator tobeginning (public member function )

cend    Return const_iterator to end (public member function )

crbegin      Return const_reverse_iterator to reversebeginning (public member function )

crend   Return const_reverse_iterator to reverse end (public member function )

这些东西和list中迭代器都类似，在list篇中已经做过大量介绍，这里就不再啰嗦了。

4：array中关于容量的函数

Capacity

size             Return size (public member function )

max_size           Return maximum size (public member function )

empty        Test whether array is empty (public member function )

4.1 size（）函数的用法，从结果中可以看出array容量的一些端倪来。

size_type size() const;

#include <iostream>

#include <array>

int main ()

{

  std::array<int,5> myints;

  std::cout << "size of myints: " << myints.size() << std::endl;

  std::cout << "sizeof(myints): " << sizeof(myints) << std::endl;

  return 0;

}

结果：

size of myints: 5

sizeof(myints): 20

4.2 max_size()函数的用法，说明这个函数和list中的max_size（）的不同

size_type max_size() const;

#include <iostream>

#include <array>

int main ()

{

  std::array<int,10> myints;

  std::cout << "size of myints: " << myints.size() << '\n';

  std::cout << "max_size of myints: " << myints.max_size() << '\n';

  return 0;

}

结果：

size of myints: 10

max_size of myints: 10

4.3empty函数

bool empty() const;

5．array中关于元素操作的函数

Element access

operator[]  Access element (public member function )

at                Access element (public member function )

front          Access first element (public member function )

back                  Access last element (public member function )

data                   Get pointer to data (public member function )

5.1operator[]操作符

reference operator[](size_type off);

const_reference operator[](size_type off) const;

示例：

#include <iostream>

#include <array>

int main ()

{

    std::array<int,10> myarray;

     unsigned int i;

    for (i=0; i<10; i++) myarray[i]=i; // assign some values:

    std::cout << "myarray contains:";  // print content

     for (i=0; i<10; i++)

    std::cout <<' '<< myarray[i];

    std::cout << '\n';

    return 0;

}

输出结果：

myarray contains: 0 1 2 3 4 5 6 7 8 9

5.2at（）函数的用法

reference at(size_type off);

const_reference at(size_type off) const;

用法：

#include <iostream>

#include <array>

int main ()

{

  std::array<int,10> myarray;

  for (int i=0; i<10; i++) 

       myarray.at(i) = i+1; // assign some values:

  std::cout << "myarray contains:" // print content:;

  for (int i=0; i<10; i++)

         std::cout << ' ' << myarray.at(i);

  std::cout << '\n';

  return 0;

}

输出结果：

myarray contains: 1 2 3 4 5 6 7 8 9 10

5.3 front函数的用法

reference front();

const_reference front() const;

示例：

#include <iostream>

#include <array>

int main ()

{

  std::array<int,3> myarray = {2, 16, 77};

  std::cout << "front is: " << myarray.front() << std::endl;   // 2

  std::cout << "back is: " << myarray.back() << std::endl;     // 77

  myarray.front() = 100;

  std::cout << "myarray now contains:";

  for ( int& x : myarray ) std::cout << ' ' << x;

  std::cout << '\n';

  return 0;

}

结果：

front is: 2

back is: 77

myarray now contains: 100 16 77

5.4 back函数的用法

reference back();

const_reference back() const;

关于例子，在5.3中的例子已经包含了

5.5 data函数的用法

Ty *data();

const Ty *data() const;

返回值指向第一个元素的指针，因为是顺序存储，所以知道了首元素的指针就可以知道所有元素了。

#include <iostream>

#include <cstring>

#include <array>

int main ()

{

  const char* cstr = "Test string";

  std::array<char,12> charray;

  std::memcpy (charray.data(),cstr,12);

  std::cout << charray.data() << '\n';

  return 0;

}

结果：

Test string

6 修改元素的函数

Modifiers

fill        Fill array with value (public member function )

swap   Swap content (public member function )

6.1 fill函数的用法

void fill(const Type& _Val);

函数将array中所有的元素替换成_val

#include <iostream>

#include <array>

int main () {

  std::array<int,6> myarray;

  myarray.fill(5);

  std::cout << "myarray contains:";

  for ( int& x : myarray) { std::cout << ' ' << x; }

  std::cout << '\n';

  return 0;

}

结果：

myarray contains: 5 5 5 5 5 5

6.2 swap函数的用法

void swap(array& right);

交换两个具有相同长度的array，切记两个array的长度必须一致

例子：

#include <iostream>

#include <array>

int main ()

{

  std::array<int,5> first = {10, 20, 30, 40, 50};

  std::array<int,5> second = {11, 22, 33, 44, 55};

  first.swap (second);

  std::cout << "first:";

  for (int& x : first) std::cout << ' ' << x;

  std::cout << '\n';

  std::cout << "second:";

  for (int& x : second) std::cout << ' ' << x;

  std::cout << '\n';

  return 0;

}

结果：

first contains: 11 22 33 44 55

second contains: 10 20 30 40 50

附加<array>头文件中其他跟array类无关的类以及函数

1：tuple_element 类

template<int Idx, class Ty, std::size_t N>

class tuple_element<Idx, <array<Ty, N> > {

    typedef Ty type;

    };

这个类就是获取array中第几个元素的值，示例如下：

#include <array> 

#include <iostream> 

 typedef std::array<int, 4> Myarray; 

int main() 

    { 

    Myarray c0 = {0, 1, 2, 3}; 

 // display contents " 0 1 2 3" 

    for (Myarray::const_iterator it = c0.begin(); 

        it != c0.end(); ++it) 

        std::cout << " " << *it; 

    std::cout << std::endl; 

// display first element " 0" 

    std::tuple_element<0, Myarray>::type val = c0.front(); 

    std::cout << " " << val; 

    std::cout << std::endl; 

     return (0); 

} 

结果：

0 1 2 3

0

2：tuple_size类

template<class Ty, std::size_t N>

class tuple_size<array<Ty, N> > {

    static const unsigned value = N;

    };

这个类就是获取array数组的大小，示例

#include <array> 

#include <iostream> 

typedef std::array<int, 4> Myarray; 

int main() 

    { 

    Myarray c0 = {0, 1, 2, 3}; 

// display contents " 0 1 2 3" 

    for (Myarray::const_iterator it = c0.begin(); 

        it != c0.end(); ++it) 

        std::cout << " " << *it; 

    std::cout << std::endl; 

 // display size " 4" 

    std::cout << " " << std::tuple_size<Myarray>::value; 

    std::cout << std::endl; 

     return (0); 

    } 

结果：

0 1 2 3

4

3：get函数的用法

template<int Idx, class Ty, std::size_t N>

    Ty& get(array<Ty, N>& arr);

template<int Idx, class Ty, std::size_t N>

    const Ty& get(const array<Ty, N>& arr);

这个函数就是返回array[id]的索引，示例

#include <array> 

#include <iostream> 

 typedef std::array<int, 4> Myarray; 

int main() 

    { 

    Myarray c0 = {0, 1, 2, 3}; 

 // display contents " 0 1 2 3" 

    for (Myarray::const_iterator it = c0.begin(); 

        it != c0.end(); ++it) 

        std::cout << " " << *it; 

    std::cout << std::endl; 

// display odd elements " 1 3" 

    std::cout << " " << std::get<1>(c0); 

    std::cout << " " << std::get<3>(c0); 

    std::cout << std::endl; 

    return (0); 

    } 

结果：

0 1 2 3

1 3

4.swap函数的用法

template<class Ty, std::size_t N>

    void swap(

        array<Ty, N>& left,

        array<Ty, N>& right);

交换两个数组的值，示例

#include <array> 

#include <iostream> 

 typedef std::array<int, 4> Myarray; 

int main() 

    { 

    Myarray c0 = {0, 1, 2, 3}; 

 // display contents " 0 1 2 3" 

    for (Myarray::const_iterator it = c0.begin(); 

        it != c0.end(); ++it) 

        std::cout << " " << *it; 

    std::cout << std::endl; 

     Myarray c1 = {4, 5, 6, 7}; 

    c0.swap(c1); 

 // display swapped contents " 4 5 6 7" 

    for (Myarray::const_iterator it = c0.begin(); 

        it != c0.end(); ++it) 

        std::cout << " " << *it; 

    std::cout << std::endl; 

     swap(c0, c1); 

 // display swapped contents " 0 1 2 3" 

    for (Myarray::const_iterator it = c0.begin(); 

        it != c0.end(); ++it) 

        std::cout << " " << *it; 

    std::cout << std::endl; 

     return (0); 

} 

结果：

 0 1 2 3

 4 5 6 7

 0 1 2 3