C++

参考

<unordered_set>

unordered_multiset

public member type
<unordered_set>

std::unordered_multiset::cbegin

container iterator (1)
const_iterator cbegin() const noexcept;
bucket iterator (2)
const_local_iterator cbegin ( size_type n ) const;
返回指向开头的 const_iterator
返回一个const_iteratorpointing to the first element in the unordered_multiset container (1) or in one of its buckets (2).

Aconst_iteratoris an iterator that points to const content. This iterator can be increased and decreased (unless it is itself also const), but it cannot be used to modify the contents it points to.

参数

n
Bucket number. This shall be lower than bucket_count.
It is an optional parameter that changes the behavior of this member function: if set, the iterator retrieved points to the first element of a bucket, otherwise it points to the first element of the container.
成员类型size_type是一种无符号整型类型。

返回值

Aconst_iteratorto the first element in the container (1) or the bucket (2).

两者都const_iterator和const_local_iteratorare member types. In the unordered_multiset class template, these are forward iterator types.
They may both be aliases of the same iterator type.

示例

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// unordered_multiset::cbegin/cend example
#include <iostream>
#include <string>
#include <unordered_set>

int main ()
{
  std::unordered_multiset<std::string> myums =
    {"father","mother","son","daughter","son","son"};

  std::cout << "myums contains:";
  for ( auto it = myums.begin(); it != myums.end(); ++it )
    std::cout << " " << *it;    // cannot modify *it
  std::cout << std::endl;

  std::cout << "myums's buckets contain:\n";
  for ( unsigned i = 0; i < myums.bucket_count(); ++i) {
    std::cout << "bucket #" << i << " contains:";
    for ( auto local_it = myums.begin(i); local_it!= myums.end(i); ++local_it )
      std::cout << " " << *local_it;
    std::cout << std::endl;
  }

  return 0;
}

可能的输出
myums contains: father mother daughter son son son
myset's buckets contain:
bucket #0 contains:
bucket #1 contains: father
bucket #2 contains: mother
bucket #3 contains: daughter son son son
bucket #4 contains: 
bucket #5 contains: 
bucket #6 contains:


复杂度

常量。

迭代器有效性

没有变化。

另见

unordered_multiset::end
返回指向末尾的迭代器 （公开成员类型）
unordered_multiset::cbegin
返回指向起始位置的 const_iterator (公开成员类型)
unordered_multiset::find
获取指向元素的迭代器 (公共成员函数)