std::deque
STD：：DEQUE
| Defined in header | | |
|---|---|---|
| template< class T, class Allocator = std::allocator<T> > class deque; | (1) | |
| namespace pmr { template <class T> using deque = std::deque<T, std::pmr::polymorphic_allocator<T>>; } | (2) | (since C++17) |
std::deque%28双结束队列%29是一个索引序列容器，它允许在开始和结束时快速插入和删除。此外，在deque的两端插入和删除不会使指针或对其余元素的引用无效。
相对于std::vector，deque的元素不是连续存储的：典型实现使用一系列单独分配的固定大小数组，并附加簿记，这意味着索引访问std：deque必须执行两个指针取消，而向量%27s索引访问只执行一个。
根据需要，自动扩展和收缩DEQE的存储。扩展一个设备比扩展一个std::vector因为它不涉及将现有元素复制到新的内存位置。另一方面，deques通常具有很大的最小内存开销；一个只包含一个元素的deque必须分配其完整的内部数组%28e.g。64位libstdc++上的对象大小是对象大小的8倍；64位libc++%29上的对象大小是对象大小的16倍或4096字节，以较大者为准。
对deques的常见操作的复杂性%28---效率%---29如下：
- 随机存取-常数O%281%29
- 在结尾或开头插入或删除元素-常数O%281%29
- 元素的插入或去除.线性O%28N%29
std::deque满足…的要求Container，，，AllocatorAwareContainer，，，SequenceContainer和ReversibleContainer...
模板参数
| T | - | The type of the elements. T must meet the requirements of CopyAssignable and CopyConstructible. (until C++11) The requirements that are imposed on the elements depend on the actual operations performed on the container. Generally, it is required that element type is a complete type and meets the requirements of Erasable, but many member functions impose stricter requirements. (since C++11) | T must meet the requirements of CopyAssignable and CopyConstructible. | (until C++11) | The requirements that are imposed on the elements depend on the actual operations performed on the container. Generally, it is required that element type is a complete type and meets the requirements of Erasable, but many member functions impose stricter requirements. | (since C++11) |
|---|---|---|---|---|---|---|
| T must meet the requirements of CopyAssignable and CopyConstructible. | (until C++11) | |||||
| The requirements that are imposed on the elements depend on the actual operations performed on the container. Generally, it is required that element type is a complete type and meets the requirements of Erasable, but many member functions impose stricter requirements. | (since C++11) | |||||
| Allocator | - | An allocator that is used to acquire/release memory and to construct/destroy the elements in that memory. The type must meet the requirements of Allocator. The behavior is undefined if Allocator::value_type is not the same as T. |
迭代器失效
本节中仍有一些不准确之处，请参阅个别成员函数页以获得更多细节。
| Operations | Invalidated |
|---|---|
| All read only operations | Never |
| swap, std::swap | The past-the-end iterator may be invalidated (implementation defined) |
| shrink_to_fit, clear, insert, emplace, push_front, push_back, emplace_front, emplace_back | Always |
| erase | If erasing at begin - only erased elements If erasing at end - only erased elements and the past-the-end iterator Otherwise - all iterators are invalidated (including the past-the-end iterator). |
| resize | If the new size is smaller than the old one : only erased elements and the past-the-end iterator If the new size is bigger than the old one : all iterators are invalidated Otherwise - none iterators are invalidated. |
| pop_front | Only to the element erased |
| pop_back | Only to the element erased and the past-the-end iterator |
失效笔记
- 在deque的两端插入时，引用不会被
insert和emplace...
push_front，，，push_back，，，emplace_front和emplace_back不要使任何对deque元素的引用无效。
- 当在deque的两端擦除时，对非擦除元素的引用不会被
erase，，，pop_front和pop_back...
- 打电话给
resize使用较小的大小，不会使任何对非擦除元素的引用失效。
- 打电话给
resize使用更大的大小不会使对deque元素的引用无效。
成员类型
| Member type | Definition |
|---|---|
| value_type | T |
| allocator_type | Allocator |
| size_type | Unsigned integer type (usually std::size_t) |
| difference_type | Signed integer type (usually std::ptrdiff_t) |
| reference | Allocator::reference (until C++11) value_type& (since C++11) |
| Allocator::reference | (until C++11) |
| value_type& | (since C++11) |
| const_reference | Allocator::const_reference (until C++11) const value_type& (since C++11) |
| Allocator::const_reference | (until C++11) |
| const value_type& | (since C++11) |
| pointer | Allocator::pointer (until C++11) std::allocator_traits<Allocator>::pointer (since C++11) |
| Allocator::pointer | (until C++11) |
| std::allocator_traits<Allocator>::pointer | (since C++11) |
| const_pointer | Allocator::const_pointer (until C++11) std::allocator_traits<Allocator>::const_pointer (since C++11) |
| Allocator::const_pointer | (until C++11) |
| std::allocator_traits<Allocator>::const_pointer | (since C++11) |
| iterator | RandomAccessIterator |
| const_iterator | Constant random access iterator |
| reverse_iterator | std::reverse_iterator<iterator> |
| const_reverse_iterator | std::reverse_iterator<const_iterator> |
成员函数
| (constructor) | constructs the deque (public member function) |
|---|---|
| (destructor) | destructs the deque (public member function) |
| operator= | assigns values to the container (public member function) |
| assign | assigns values to the container (public member function) |
| get_allocator | returns the associated allocator (public member function) |
元素存取
在访问指定元素时，使用边界检查%28公共成员函数%29
操作者。[]访问指定元素%28公共成员函数%29
前端访问第一个元素%28公共成员函数%29
返回访问最后一个元素%28公共成员函数%29
迭代器
BEGINCBEGIN将迭代器返回到开头%28的公共成员函数%29
End cend将迭代器返回到End%28公共成员函数%29
将反向迭代器返回到开头%28的公共成员函数%29
rend crend将反向迭代器返回到End%28公共成员函数%29
容量
空检查容器是否为空%28公共成员函数%29
Size返回元素数%28公共成员函数%29
马克斯[医]Size返回元素的最大可能数%28公共成员函数%29
收缩[医]到[医]FIT%28C++11%29通过释放未使用内存%28公共成员函数%29来减少内存使用
修饰符
清除内容%28公共成员功能%29
插入元素%28公共成员函数%29
嵌入%28C++11%29构造元素就地%28公共成员函数%29
擦除元素%28公共成员函数%29
推[医]向末尾%28公共成员函数%29添加一个元素
座落[医]Back%28C++11%29在%28公共成员函数%29的末尾构造一个就地元素。
波普[医]回移除最后一个元素%28公共成员函数%29
推[医]前端插入元素到开头%28公共成员函数%29
座落[医]前端%28c++11%29在开始处构造一个元素(%28公共成员函数%29)。
波普[医]前端移除第一个元素%28公共成员函数%29
调整大小更改存储的元素数%28公共成员函数%29
交换交换内容%28公共成员函数%29
非会员职能
| operator==operator!=operator | lexicographically compares the values in the deque (function template) |
|---|---|
| std::swap(std::deque) | specializes the std::swap algorithm (function template) |
例
二次
#include <iostream>
#include <deque>
int main()
{
// Create a deque containing integers
std::deque<int> d = {7, 5, 16, 8};
// Add an integer to the beginning and end of the deque
d.push_front(13
d.push_back(25
// Iterate and print values of deque
for(int n : d) {
std::cout << n << '\n';
}
}
二次
产出：
二次
13
7
5
16
8
25
二次
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