std::unordered_multiset::unordered_multiset

(1) empty container constructor (default constructor)

Constructs an empty unordered_multiset object, containing no elements and with a size of zero.
It can construct the container with specific hasher, key_equal and allocator objects, along with a minimum number of hash buckets.

(2) 范围构造函数 ((2) range constructor)

Constructs an unordered_multiset object containing copies of each of the elements in the range[first,last).

(3) copy constructor (and copying with allocator)

The object is initialized to have the same contents and properties as the ums unordered_multiset object.

(4) move constructor (and moving with allocator)

The object acquires the contents of the rvalue ums.

(5) initializer list

Initializes the container with the contents of the list.

参数

n

Minimum number of initial buckets.
This is not the number of elements in the container, but the minimum number of slots desired for the internal hash table on construction.
If this argument is not specified, the constructor determines this automatically (in a way that depends on the particular library implementation).
成员类型size_type是一种无符号整型类型。

hf

Hasher function object. A hasher is a function that returns an integral value based on the container object key passed to it as argument.
成员类型hasheris defined in unordered_multiset as an alias of its second template parameter (Hash).

eql

Comparison function object, that returnstrueif the two container object keys passed as arguments are to be considered equal.
成员类型key_equalis defined in unordered_multiset as an alias of its third template parameter (Pred).

alloc

要使用的分配器对象，而不是构造一个新的分配器对象。
对于使用其默认 分配器类模板版本的类实例化，此参数不相关。
成员类型allocator_typeis defined in unordered_multiset as an alias of its fourth template parameter (Alloc).

first, last

指向范围内初始位置和最终位置的输入迭代器。 使用的范围是[first,last)，它包括first和last之间的所有元素，包括first指向的元素，但不包括last指向的元素。
The function template type can be any type of input iterator.

ums

Another unordered_multiset object of the same type (with the same class template arguments), whose contents are either copied or moved.

il

il
这些对象是从初始化列表声明符自动构造的。
成员类型value_typeis the type of the elements in the container, defined in unordered_multiset as an alias of the first template parameter (键).

示例

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// constructing unordered_multisets
#include <iostream>
#include <string>
#include <unordered_set>

template<class T>
T cmerge (T a, T b) { T t(a); t.insert(b.begin(),b.end()); return t; }

int main ()
{
  std::unordered_multiset<std::string> first;                                // empty
  std::unordered_multiset<std::string> second ( {"red","green","blue"} );    // init list
  std::unordered_multiset<std::string> third ( {"red","yellow","blue"} );    // init list
  std::unordered_multiset<std::string> fourth ( second );                    // copy
  std::unordered_multiset<std::string> fifth ( cmerge(third,fourth) );       // move
  std::unordered_multiset<std::string> sixth ( fifth.begin(), fifth.end() ); // range

  std::cout << "sixth contains:";
  for (const std::string& x: sixth) std::cout << " " << x;
  std::cout << std::endl;

  return 0;
}

sixth contains: yellow red red green blue blue

复杂度

另见

unordered_multiset::operator=

赋新值 (公开成员函数)

unordered_multiset::insert

插入元素 (公开成员函数)

unordered_multiset::reserve

请求容量更改 (公共成员函数)