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Std::Map:: Max_Size

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Equivalent to return this->try_emplace(std::move(key)).first->second;.(since C++17) When the default allocator is used, this results in the key being move constructed from key and the mapped value being value-initialized. This value typically allows calling this function reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available.

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This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). 异常 调用 Allocator allocate 可能会抛出异常 At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available.

std::map<Key,T,Compare,Allocator>::size_C++中文网

This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available. Erases all elements from the container. After this call, size () returns zero.

Constructs new container from a variety of data sources and optionally using user supplied allocator alloc or comparison function object comp.

Notes This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max (). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available. to return this try_emplace std::map is a sorted associative container that contains key-value pairs with unique keys. Keys are sorted by using the comparison function Compare. Search, removal, and insertion operations have logarithmic complexity. Maps are usually implemented as

  • std::map<Key,T,Compare,Allocator>:: value_compare
  • std::map<Key,T,Compare,Allocator>::clear
  • std::map<Key,T,Compare,Allocator>:: value_comp

Returns the number of elements in the container, i.e. std::distance(begin(), end()). Parameters (none) Return value The number of elements in the container. Complexity Constant. Example The following code uses size to display the number of elements in a std::map:

std::map is a sorted associative container that contains key-value pairs with unique keys. Keys are sorted by using the comparison function Compare. Search, removal, and insertion operations have logarithmic complexity. Maps are usually implemented as

This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available. This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). container may be limited At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available. This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available.

std::map<Key,T,Compare,Allocator>:: value_compare

This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value a value smaller smaller than max_size () by the amount of RAM available. std::map:: map 从各种数据源构造新容器，可选地使用用户提供的分配器 alloc 或比较函数对象 comp 。 1) 构造空容器。 2) 构造容器，使之拥有范围 [first, last) 的内容。

This overload participates in overload resolution only if Compare is transparent. It allows calling this function without constructing an instance of Key. This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available.

This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). the comparison function At runtime, the size of the container may be limited to a value smaller than max_size() by the amount of RAM available.

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This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available.

返回容器中的元素数，即 std::distance(begin(), end()) 。 参数 （无） 返回值 容器中的元素数量。 复杂度 常数。 示例 下列代码用 size 显示 std::map 中的元素数： 运行此代码

This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available. 异常 调用 Allocator::allocate 可能会抛出异常。 注意 容器移动构造（重载 (8,9)）之后，对 other 的引用、指针和迭代器（末尾迭代器除外）仍然有效，但引用现在位于 *this 中的元素。当前标准通过 [container.reqmts]/67 中的一般性声明以及通过 LWG issue 2321 正在考虑更直接的保证来做出此保证。 虽然在 C++23 std::map 是有序键值对容器，它的元素的键是唯一的。 用比较函数 Compare 排序键。 搜索、移除和插入操作拥有对数复杂度。 map 通常实现为 红黑树。 在每个标准库使用 比较 (Compare) 概念的位置，以等价关系检验唯一性。

std::map<Key,T,Compare,Allocator>::max_size

此值通常反映容器大小上的理论极限，至多为 std::numeric_limits::max()。 运行时，可用 RAM 总量可能会限制容器大小到小于 max_size () 的值。 This value typically reflects the theoretical limit on the size of the container, that contains at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available.

std::map 的所有成员函数都是 constexpr：可以在常量表达式的求值中创建和使用 std::map 对象。 但是， std::map 对象通常不能是 constexpr，因为任何动态分配的存储都必须在相同的常量表达式求值中释放。 (since C++26) std::map is a sorted associative container that contains key-value pairs with unique keys. Keys are sorted by using the comparison function Compare. Search, removal, and insertion operations have logarithmic complexity. Maps are usually implemented as red-black trees. Template parameters Key Type of the keys. Each element in a map is uniquely identified by its key value. Aliased as member type map::key_type. T Type of the mapped value. Each element in a map stores some data as its mapped value. Aliased as member type map::mapped_type. Compare A binary predicate that takes two element keys as arguments and returns a bool. The

Member functions map::map map::~map map::operator= map::get_allocator Element access map::at map::operator [] Iterators map::beginmap::cbegin (C++11) map::endmap

This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available. Member functions map::map map::~map map::operator= map::get_allocator Element access map::at map::operator [] Iterators map::beginmap::cbegin (C++11) map::endmap

std::map::value_compare is a function object that compares objects of type std::map::value_type (key-value pairs) by comparing of the first components of the pairs.

std::map<Key,T,Compare,Allocator>::size

This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits::max(). At runtime, the size of the container may be limited to a value smaller than max_size () by the amount of RAM available.