public member function
<set>
iterator begin();const_iterator begin() const;
iterator begin() noexcept;const_iterator begin() const noexcept;
Return iterator to beginning
Returns an iterator referring to the first element in the multiset container.
Because multiset containers keep their elements ordered at all times,beginpoints to the element that goes first following the container's sorting criterion.
If the container is empty, the returned iterator value shall not be dereferenced.
返回值
指向容器中第一个元素的迭代器。
If the multiset object is const-qualified, the function returns aconst_iterator。否则，它返回一个iterator.
成员类型iterator和const_iteratorare bidirectional iterator types pointing to elements.
示例
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// multiset::begin/end
#include <iostream>
#include <set>
int main ()
{
int myints[] = {42,71,71,71,12};
std::multiset<int> mymultiset (myints,myints+5);
std::multiset<int>::iterator it;
std::cout << "mymultiset contains:";
for (std::multiset<int>::iterator it=mymultiset.begin(); it!=mymultiset.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
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输出
mymultiset contains: 12 42 71 71 71
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数据竞争
访问容器（const 和非 const 版本都不会修改容器）。
同时访问 multiset 的元素是安全的。
异常安全
无异常保证：此成员函数从不抛出异常。
还可以保证返回的迭代器的复制构造或赋值永远不会引发异常。