vector::begin

最新推荐文章于 2024-10-20 19:42:24 发布

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#vector #begin

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本文介绍了C++标准库中vector容器的begin()方法，该方法返回指向容器首元素的随机访问迭代器。通过示例代码展示了如何使用迭代器遍历vector容器中的所有元素。

Return iterator to beginning

Returns an iterator pointing to the first element in the vector.

Notice that, unlike member vector::front, which returns a reference to the first element, this function returns arandom access iterator pointing to it.

If the container is empty, the returned iterator value shall not be dereferenced.

Parameters(参数)

none

Return Value

An iterator to the beginning of the sequence container.

If the vector object is const-qualified, the function returns a const_iterator. Otherwise, it returns an iterator.

Member types iterator and const_iterator are random access iterator types (pointing to an element and to a const element, respectively).

// vector::begin/end
#include <iostream>
#include <vector>
using namespace std;
int main ()
{
  vector<int> myvector;
  for (int i=1; i<=5; i++) myvector.push_back(i);

  cout << "myvector contains:";
  for (vector<int>::iterator it = myvector.begin() ; it != myvector.end(); ++it)
   cout << ' ' << *it;
    cout << endl;
  return 0;
}

---------------------------------------------------

// vector::begin/end
#include <iostream>
#include <vector>
using namespace std;
int main ()
{
  vector<int> myvector;
  for (int i=1; i<=5; i++) myvector.push_back(i);

  cout << "myvector contains:";
  vector<int>::iterator it;
  
  for (it = myvector.begin() ; it != myvector.end(); ++it)
   cout << ' ' << *it;
    cout << endl;
  return 0;
}

Output: