C++

Reference

<vector>

vector

public member function
<vector>

std::vector::size

size_type size() const;
size_type size() const noexcept;
Return size
Returns the number of elements in the vector.

This is the number of actual objects held in the vector, which is not necessarily equal to its storage capacity.

Parameters

none

Return Value

The number of elements in the container.

Member type size_type is an unsigned integral type.

Example

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// vector::size
#include <iostream>
#include <vector>

int main ()
{
  std::vector<int> myints;
  std::cout << "0. size: " << myints.size() << '\n';

  for (int i=0; i<10; i++) myints.push_back(i);
  std::cout << "1. size: " << myints.size() << '\n';

  myints.insert (myints.end(),10,100);
  std::cout << "2. size: " << myints.size() << '\n';

  myints.pop_back();
  std::cout << "3. size: " << myints.size() << '\n';

  return 0;
}

Output:
0. size: 0
1. size: 10
2. size: 20
3. size: 19


Complexity

Constant.

Iterator validity

No changes.

Data races

The container is accessed.
No contained elements are accessed: concurrently accessing or modifying them is safe.

Exception safety

No-throw guarantee: this member function never throws exceptions.

See also

vector::capacity
Return size of allocated storage capacity (public member function)
vector::resize
Change size (public member function)
vector::max_size
Return maximum size (public member function)