std::vector<T,Allocator>::begin, std::vector<T,Allocator>::cbegin
From cppreference.com
iterator begin(); |
(1) | (noexcept since C++11) (constexpr since C++20) |
const_iterator begin() const; |
(2) | (noexcept since C++11) (constexpr since C++20) |
const_iterator cbegin() const noexcept; |
(3) | (since C++11) (constexpr since C++20) |
Returns an iterator to the first element of the vector.
If the vector is empty, the returned iterator will be equal to end().
Return value
Iterator to the first element.
Complexity
Constant.
Notes
libc++ backports cbegin() to C++98 mode.
Example
Run this code
#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.
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) |