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Containers library
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operators (std::array)
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operators (std::unordered_set)
operators (std::vector)
remove_if
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std::array
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std::array::empty
std::array::end
std::array::fill
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std::array::max_size
std::array::operator[]
std::array::rbegin
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std::array::size
std::array::swap
std::deque
std::deque::assign
std::deque::at
std::deque::back
std::deque::begin
std::deque::cbegin
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std::deque::crend
std::deque::deque
std::deque::emplace
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std::deque::emplace_front
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std::deque::erase
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std::deque::get_allocator
std::deque::insert
std::deque::max_size
std::deque::operator[]
std::deque::pop_back
std::deque::pop_front
std::deque::push_back
std::deque::push_front
std::deque::rbegin
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std::deque::resize
std::deque::shrink_to_fit
std::deque::size
std::deque::swap
std::forward_list
std::forward_list::assign
std::forward_list::before_begin
std::forward_list::begin
std::forward_list::cbegin
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std::forward_list::clear
std::forward_list::emplace_after
std::forward_list::emplace_front
std::forward_list::empty
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std::forward_list::erase_after
std::forward_list::forward_list
std::forward_list::front
std::forward_list::get_allocator
std::forward_list::insert_after
std::forward_list::max_size
std::forward_list::merge
std::forward_list::pop_front
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std::forward_list::reverse
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std::forward_list::unique
std::get(std::array)
std::hash
std::list
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std::list::back
std::list::begin
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std::list::emplace_front
std::list::empty
std::list::end
std::list::erase
std::list::front
std::list::get_allocator
std::list::insert
std::list::list
std::list::max_size
std::list::merge
std::list::pop_back
std::list::pop_front
std::list::push_back
std::list::push_front
std::list::rbegin
std::list::remove
std::list::rend
std::list::resize
std::list::reverse
std::list::size
std::list::sort
std::list::splice
std::list::swap
std::list::unique
std::map
std::map::at
std::map::begin
std::map::cbegin
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std::map::clear
std::map::count
std::map::crbegin
std::map::crend
std::map::emplace
std::map::emplace_hint
std::map::empty
std::map::end
std::map::equal_range
std::map::erase
std::map::extract
std::map::find
std::map::get_allocator
std::map::insert
std::map::insert_or_assign
std::map::key_comp
std::map::lower_bound
std::map::map
std::map::max_size
std::map::merge
std::map::operator[]
std::map::rbegin
std::map::rend
std::map::size
std::map::swap
std::map::try_emplace
std::map::upper_bound
std::map::value_comp
std::map::value_compare
std::multimap
std::multimap::begin
std::multimap::cbegin
std::multimap::cend
std::multimap::clear
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std::multimap::crend
std::multimap::emplace
std::multimap::emplace_hint
std::multimap::empty
std::multimap::end
std::multimap::equal_range
std::multimap::erase
std::multimap::extract
std::multimap::find
std::multimap::get_allocator
std::multimap::insert
std::multimap::key_comp
std::multimap::lower_bound
std::multimap::max_size
std::multimap::merge
std::multimap::multimap
std::multimap::rbegin
std::multimap::rend
std::multimap::size
std::multimap::swap
std::multimap::upper_bound
std::multimap::value_comp
std::multimap::value_compare
std::multiset
std::multiset::begin
std::multiset::cbegin
std::multiset::cend
std::multiset::clear
std::multiset::count
std::multiset::crbegin
std::multiset::crend
std::multiset::emplace
std::multiset::emplace_hint
std::multiset::empty
std::multiset::end
std::multiset::equal_range
std::multiset::erase
std::multiset::extract
std::multiset::find
std::multiset::get_allocator
std::multiset::insert
std::multiset::key_comp
std::multiset::lower_bound
std::multiset::max_size
std::multiset::merge
std::multiset::multiset
std::multiset::rbegin
std::multiset::rend
std::multiset::size
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std::multiset::upper_bound
std::multiset::value_comp
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std::priority_queue::pop
std::priority_queue::priority_queue
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std::priority_queue::size
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std::priority_queue::top
std::queue
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std::queue::emplace
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std::queue::queue
std::queue::size
std::queue::swap
std::set
std::set::begin
std::set::cbegin
std::set::cend
std::set::clear
std::set::count
std::set::crbegin
std::set::crend
std::set::emplace
std::set::emplace_hint
std::set::empty
std::set::end
std::set::equal_range
std::set::erase
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std::set::find
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std::set::key_comp
std::set::lower_bound
std::set::max_size
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std::set::rbegin
std::set::rend
std::set::set
std::set::size
std::set::swap
std::set::upper_bound
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std::stack
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std::stack::size
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std::swap(std::array)
std::swap(std::deque)
std::swap(std::forward_list)
std::swap(std::list)
std::swap(std::map)
std::swap(std::multimap)
std::swap(std::multiset)
std::swap(std::priority_queue)
std::swap(std::queue)
std::swap(std::set)
std::swap(std::stack)
std::swap(std::unordered_map)
std::swap(std::unordered_multimap)
std::swap(std::unordered_multiset)
std::swap(std::unordered_set)
std::swap(std::vector)
std::tuple_element<std::array>
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std::unordered_map
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std::unordered_map::cend
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std::unordered_map::count
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std::unordered_map::empty
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std::unordered_map::end(int)
std::unordered_map::equal_range
std::unordered_map::erase
std::unordered_map::extract
std::unordered_map::find
std::unordered_map::get_allocator
std::unordered_map::hash_function
std::unordered_map::insert
std::unordered_map::insert_or_assign
std::unordered_map::key_eq
std::unordered_map::load_factor
std::unordered_map::max_bucket_count
std::unordered_map::max_load_factor
std::unordered_map::max_size
std::unordered_map::merge
std::unordered_map::operator[]
std::unordered_map::rehash
std::unordered_map::reserve
std::unordered_map::size
std::unordered_map::swap
std::unordered_map::try_emplace
std::unordered_map::unordered_map
std::unordered_multimap
std::unordered_multimap::begin
std::unordered_multimap::begin(int)
std::unordered_multimap::bucket
std::unordered_multimap::bucket_count
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std::unordered_multimap::cbegin
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std::unordered_multimap::empty
std::unordered_multimap::end
std::unordered_multimap::end(int)
std::unordered_multimap::equal_range
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std::unordered_multimap::find
std::unordered_multimap::get_allocator
std::unordered_multimap::hash_function
std::unordered_multimap::insert
std::unordered_multimap::key_eq
std::unordered_multimap::load_factor
std::unordered_multimap::max_bucket_count
std::unordered_multimap::max_load_factor
std::unordered_multimap::max_size
std::unordered_multimap::merge
std::unordered_multimap::rehash
std::unordered_multimap::reserve
std::unordered_multimap::size
std::unordered_multimap::swap
std::unordered_multimap::unordered_multimap
std::unordered_multiset
std::unordered_multiset::begin
std::unordered_multiset::begin(int)
std::unordered_multiset::bucket
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std::unordered_multiset::bucket_size
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std::unordered_multiset::end(int)
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std::unordered_multiset::insert
std::unordered_multiset::key_eq
std::unordered_multiset::load_factor
std::unordered_multiset::max_bucket_count
std::unordered_multiset::max_load_factor
std::unordered_multiset::max_size
std::unordered_multiset::merge
std::unordered_multiset::rehash
std::unordered_multiset::reserve
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std::unordered_multiset::swap
std::unordered_multiset::unordered_multiset
std::unordered_set
std::unordered_set::begin
std::unordered_set::begin(int)
std::unordered_set::bucket
std::unordered_set::bucket_count
std::unordered_set::bucket_size
std::unordered_set::cbegin
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std::unordered_set::cend
std::unordered_set::cend
std::unordered_set::clear
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std::unordered_set::empty
std::unordered_set::end
std::unordered_set::end(int)
std::unordered_set::equal_range
std::unordered_set::erase
std::unordered_set::extract
std::unordered_set::find
std::unordered_set::get_allocator
std::unordered_set::hash_function
std::unordered_set::insert
std::unordered_set::key_eq
std::unordered_set::load_factor
std::unordered_set::max_bucket_count
std::unordered_set::max_load_factor
std::unordered_set::max_size
std::unordered_set::merge
std::unordered_set::rehash
std::unordered_set::reserve
std::unordered_set::size
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std::uses_allocator<std::queue>
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std::vector::data
std::vector::emplace
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std::vector::end
std::vector::erase
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std::vector::reserve

STD：：载体：：储备金

void reserve( size_type new_cap ​​

将容器容量提高到大于或等于%27s的值new_cap.如果new_cap大于当前capacity()，则分配新存储空间，否则该方法将不执行任何操作。

如果new_cap大于capacity()，所有迭代器，包括过去的结束迭代器，以及所有对元素的引用都无效.。否则，没有迭代器或引用无效。

参数

new_cap-new capacity of the container

类型要求

-T必须符合MoveInserable的要求。

返回值

%280%29

例外

  • std::length_error如果new_cap > max_size()...

  • 引发的任何异常Allocator::allocate()%28典型std::bad_alloc%29

复杂性

最多是线性的size()集装箱的。

注记

reserve()不能用于减少集装箱的容量，为此目的shrink_to_fit()提供。

正确使用reserve()可以防止不必要的重新分配，但不适当地使用reserve()%28例如，在每个push_back()调用%#number0#实际上增加了重分配的数量%28，因为它导致容量线性增长，而不是指数增长的%29，从而导致计算复杂度的增加和性能的下降。

例

二次

#include <cstddef>
#include <new>
#include <vector>
#include <iostream>
 
// minimal C++11 allocator with debug output
template <class Tp>
struct NAlloc {
    typedef Tp value_type;
    NAlloc() = default;
    template <class T> NAlloc(const NAlloc<T>&) {}
    Tp* allocate(std::size_t n) {
        n *= sizeof(Tp
        std::cout << "allocating " << n << " bytes\n";
        return static_cast<Tp*>(::operator new(n)
    }
    void deallocate(Tp* p, std::size_t n) {
        std::cout << "deallocating " << n*sizeof*p << " bytes\n";
        ::operator delete(p
    }
};
template <class T, class U>
bool operator==(const NAlloc<T>&, const NAlloc<U>&) { return true; }
template <class T, class U>
bool operator!=(const NAlloc<T>&, const NAlloc<U>&) { return false; }
 
int main()
{
    int sz = 100;
    std::cout << "using reserve: \n";
    {
        std::vector<int, NAlloc<int>> v1;
        v1.reserve(sz
        for(int n = 0; n < sz; ++n)
            v1.push_back(n
    }
    std::cout << "not using reserve: \n";
    {
        std::vector<int, NAlloc<int>> v1;
        for(int n = 0; n < sz; ++n)
            v1.push_back(n
    }
}

二次

可能的产出：

二次

using reserve: 
allocating 400 bytes
deallocating 400 bytes
not using reserve: 
allocating 4 bytes
allocating 8 bytes
deallocating 4 bytes
allocating 16 bytes
deallocating 8 bytes
allocating 32 bytes
deallocating 16 bytes
allocating 64 bytes
deallocating 32 bytes
allocating 128 bytes
deallocating 64 bytes
allocating 256 bytes
deallocating 128 bytes
allocating 512 bytes
deallocating 256 bytes
deallocating 512 bytes

二次

另见

capacityreturns the number of elements that can be held in currently allocated storage (public member function)
max_sizereturns the maximum possible number of elements (public member function)
resizechanges the number of elements stored (public member function)
shrink_to_fit (C++11)reduces memory usage by freeing unused memory (public member function)

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