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std::deque<T,Allocator>::begin, std::deque<T,Allocator>::cbegin

(1) 
iterator begin();
 (until C++11) 
iterator begin() noexcept;
 (since C++11)
(2) 
const_iterator begin() const;
 (until C++11) 
const_iterator begin() const noexcept;
 (since C++11) 
const_iterator cbegin() const noexcept;
 (3) (since C++11)

Returns an iterator to the first element of the deque.

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

range-begin-end.svg

Parameters

(none).

Return value

Iterator to the first element.

Complexity

Constant.

Example

#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";
}

Output:

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

See also

(C++11)
 returns an iterator to the end
(public member function)
(C++11)(C++14)
 returns an iterator to the beginning of a container or array
(function template)

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