std::deque end()/cend() method

od C++11

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

uwaga

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

.

Parameters

(none)

Return value

Iterator to the past-the-end element.

Complexity

Constant - O(1).

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 <deque>
#include <string>

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

cend

#include <deque>
#include <string>

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

Const container

end

#include <deque>
#include <string>

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

cend

#include <deque>
#include <string>

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

Example

Main.cpp

#include <algorithm>
#include <iostream>
#include <numeric>
#include <string>
#include <deque>

int main()
{
    std::deque<int> nums {1, 2, 4, 8, 16};
    std::deque<std::string> fruits {"orange", "apple", "raspberry"};
    std::deque<char> empty;

    // Print deque.
    std::for_each(nums.begin(), nums.end(), [](const int n) { std::cout << n << ' '; });
    std::cout << '\n';

    // Sums all integers in the deque 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 deque fruits, checking if there is any.
    if (!fruits.empty())
        std::cout << "First fruit: " << *fruits.begin() << '\n';

    if (empty.begin() == empty.end())
        std::cout << "deque 'empty' is indeed empty.\n";
}

Possible Output

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