std::vector end() method

od C++20

// prism-push-types:iterator,const_iterator
// Non-const version
constexpr iterator        end() noexcept;

// Const version
constexpr const_iterator  end() const noexcept;
constexpr const_iterator  cend() const noexcept;

od C++11

// prism-push-types:iterator,const_iterator
// Non-const version
iterator        end() noexcept;

// Const version
const_iterator  end() const noexcept;
const_iterator  cend() const noexcept;

do C++11

// Non-const version
iterator        end();

// Const version
const_iterator  end() const;

Returns an iterator

to the element past-the-end of the array.

If the array is empty, the returned iterator will be equal to begin().

Undefined Behaviour

Attempting to dereference a past-the-end iterator is undefined behavior

.

Parameters

(none)

Return value

Iterator to the first element.

Complexity

Constant - O(1).

Notes

For a container c, the expression *c.begin() is equivalent to c.front().

Difference between end and cend

For a const container c, end and cend are the same - c.end() == c.cend()

For non-const container of type c they return different iterators:

Non const container

end

#include <vector>

int main()
{
    std::vector<int> arr = {1, 2, 3, 4, 5};
    auto it = arr.end(); // Type: std::vector<int>::iterator
    *std::prev(it) = 5; // ✔ Ok
}

cend

#include <vector>

int main()
{
    std::vector<int> arr = {1, 2, 3, 4, 5};
    auto it = arr.cend(); // Type: std::vector<int>::const_iterator
    *std::prev(it) = 5; // ❌ Error! 
}

Const container

end

#include <vector>

int main()
{
    const std::vector<int> arr = {1, 2, 3, 4, 5};
    auto it = arr.end(); // Type: std::vector<int>::const_iterator
    *std::prev(it) = 5; // ❌ Error! 
}

cend

#include <vector>

int main()
{
    const std::vector<int> arr = {1, 2, 3, 4, 5};
    auto it = arr.cend(); // Type: std::vector<int>::const_iterator
    *std::prev(it) = 5; // ❌ Error! 
}

Example

Main.cpp

#include <algorithm>
#include <iostream>
#include <numeric>
#include <string>
#include <vector>
 
int main()
{
    std::vector<int> nums {1, 2, 4, 8, 16};
    std::vector<std::string> fruits {"orange", "apple", "raspberry"};
    std::vector<char> empty;
 
    // Print vector.
    std::for_each(nums.begin(), nums.end(), [](const int n) { std::cout << n << ' '; });
    std::cout << '\n';
 
    // Sums all integers in the vector nums (if any), printing only the result.
    std::cout << "Sum of nums: "
              << std::accumulate(nums.begin(), nums.end(), 0) << '\n';
 
    // Prints the first fruit in the vector fruits, checking if there is any.
    if (!fruits.empty())
        std::cout << "First fruit: " << *fruits.begin() << '\n';
 
    if (empty.begin() == empty.end())
        std::cout << "vector 'empty' is indeed empty.\n";
}

Output

1 2 4 8 16
Sum of nums: 31
First fruit: orange
vector 'empty' is indeed empty.