双向队列Constructors构造函数运用

Constructors
语法:

deque();

deque( size_type size );

deque( size_type num, const TYPE &val );

deque( const deque &from );

deque( input_iterator start, input_iterator end );

C++ Deques能用以下方式创建:

无参，创建一个空双向队列
size – 创建一个大小为size的双向队列
num and val – 放置num个val的拷贝到队列中，
from – 从from创建一个内容一样的双向队列
start 和 end – 创建一个队列，保存从start到end的元素。

下列代码创建并显示一个双向队列：

//源代码

/**

* @brief Default constructor creates no elements.

explicit

deque(const allocator_type& __a = allocator_type())

: _Base(__a, 0) {}

/**

* @brief Create a %deque with copies of an exemplar element.

* @param n The number of elements to initially create.

* @param value An element to copy.

* This constructor fills the %deque with @a n copies of @a value.

deque(size_type __n, const value_type& __value,

const allocator_type& __a = allocator_type())

: _Base(__a, __n)

{ _M_fill_initialize(__value); }

/**

* @brief Create a %deque with default elements.

* @param n The number of elements to initially create.

* This constructor fills the %deque with @a n copies of a

* default-constructed element.

explicit

deque(size_type __n)

: _Base(allocator_type(), __n)

{ _M_fill_initialize(value_type()); }

/**

* @brief %Deque copy constructor.

* @param x A %deque of identical element and allocator types.

* The newly-created %deque uses a copy of the allocation object used

* by @a x.

deque(const deque& __x)

: _Base(__x.get_allocator(), __x.size())

{ std::uninitialized_copy(__x.begin(), __x.end(), this->_M_impl._M_start); }

/**

* @brief Builds a %deque from a range.

* @param first An input iterator.

* @param last An input iterator.

* Create a %deque consisting of copies of the elements from [first,

* last).

* If the iterators are forward, bidirectional, or random-access, then

* this will call the elements' copy constructor N times (where N is

* distance(first,last)) and do no memory reallocation. But if only

* input iterators are used, then this will do at most 2N calls to the

* copy constructor, and logN memory reallocations.

template<typename _InputIterator>

deque(_InputIterator __first, _InputIterator __last,

const allocator_type& __a = allocator_type())

: _Base(__a)

{

// Check whether it's an integral type. If so, it's not an iterator.

typedef typename _Is_integer<_InputIterator>::_Integral _Integral;

_M_initialize_dispatch(__first, __last, _Integral());

}

测试代码：

测试结果：

dq2双向对列：
0 0 0 0 0 0 0 0 0 0
dq3双向对列：
1 1 1 1 1
dq4双向对列：
1 1 1 1 1
dq5双向对列：
1 1 1 1 1
请按任意键继续. . .

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