std::vector<T,Allocator>:: rbegin, std::vector<T,Allocator>:: crbegin
reverse_iterator rbegin
(
)
;
|
(1) |
(noexcept since C++11)
(constexpr since C++20) |
const_reverse_iterator rbegin
(
)
const
;
|
(2) |
(noexcept since C++11)
(constexpr since C++20) |
const_reverse_iterator crbegin
(
)
const
noexcept
;
|
(3) |
(since C++11)
(constexpr since C++20) |
Returns a reverse iterator to the first element of the reversed
vector
. It corresponds to the last element of the non-reversed
vector
. If the
vector
is empty, the returned iterator is equal to
rend()
.
Parameters
(none)
Return value
Reverse iterator to the first element.
Complexity
Constant.
Notes
The underlying iterator of the returned reverse iterator is the end iterator . Hence the returned iterator is invalidated if and when the end iterator is invalidated.
libc++ backports
crbegin()
to C++98 mode.
Example
#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.rbegin(), nums.rend(), [](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.rbegin(), nums.rend(), 0) << '\n'; // Prints the first fruit in the vector fruits, checking if there is any. if (!fruits.empty()) std::cout << "First fruit: " << *fruits.rbegin() << '\n'; if (empty.rbegin() == empty.rend()) std::cout << "vector 'empty' is indeed empty.\n"; }
Output:
16 8 4 2 1 Sum of nums: 31 First fruit: raspberry vector 'empty' is indeed empty.
See also
(C++11)
|
returns a reverse iterator to the end
(public member function) |
(C++14)
|
returns a reverse iterator to the beginning of a container or array
(function template) |