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std::deque<T,Allocator>::rbegin, std::deque<T,Allocator>::crbegin

From cppreference.com
< cpp‎ | container‎ | deque
 
 
Containers library
Sequence
(C++11)
Associative
Unordered associative
Adaptors
Views
(C++20)
 
 
reverse_iterator rbegin();
(until C++11)
reverse_iterator rbegin() noexcept;
(since C++11)
const_reverse_iterator rbegin() const;
(until C++11)
const_reverse_iterator rbegin() const noexcept;
(since C++11)
const_reverse_iterator crbegin() const noexcept;
(since C++11)

Returns a reverse iterator to the first element of the reversed deque. It corresponds to the last element of the non-reversed deque. If the deque is empty, the returned iterator is equal to rend().

range-rbegin-rend.svg

Contents

[edit] Parameters

(none)

[edit] Return value

Reverse iterator to the first element.

[edit] Complexity

Constant.


[edit] 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.rbegin(), nums.rend(), [](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.rbegin(), nums.rend(), 0) << '\n';
 
    // Prints the first fruit in the deque fruits, checking if there is any.
    if (!fruits.empty())
        std::cout << "First fruit: " << *fruits.rbegin() << '\n';
 
    if (empty.rbegin() == empty.rend())
        std::cout << "deque 'empty' is indeed empty.\n";
}

Output:

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

[edit] See also

returns a reverse iterator to the end
(public member function) [edit]