std::deque<T,Allocator>::begin,std::deque<T,Allocator>::cbegin
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std::deque
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iterator begin(); | (1) | (noexcept since C++11) (constexpr since C++26) |
const_iterator begin()const; | (2) | (noexcept since C++11) (constexpr since C++26) |
const_iterator cbegin()constnoexcept; | (3) | (since C++11) (constexpr since C++26) |
Returns an iterator to the first element of*this.
If*this is empty, the returned iterator will be equal toend().
Contents |
[edit]Return value
Iterator to the first element.
[edit]Complexity
Constant.
Notes
libc++ backportscbegin() to C++98 mode.
[edit]Example
Run this code
#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(),[](constint 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 16Sum of nums: 31First fruit: orangedeque 'empty' is indeed empty.
[edit]See also
(C++11) | returns an iterator to the end (public member function)[edit] |
(C++11)(C++14) | returns an iterator to the beginning of a container or array (function template)[edit] |
