std::list<T,Allocator>::begin, std::list<T,Allocator>::cbegin
來自 cppreference.com
iterator begin(); |
(1) | (C++11 起無異常丟擲) |
const_iterator begin() const; |
(2) | (C++11 起無異常丟擲) |
const_iterator cbegin() const noexcept; |
(3) | (C++11 起) |
返回指向 `list` 首元素的迭代器。
若 `list` 為空,則返回的迭代器將等於 end()。
目錄 |
[編輯] 返回值
指向第一個元素的迭代器。
[編輯] 複雜度
常數時間。
注意
libc++ 將 cbegin()
後向移植到 C++98 模式。
[編輯] 示例
執行此程式碼
#include <algorithm> #include <iostream> #include <numeric> #include <string> #include <list> int main() { std::list<int> nums{1, 2, 4, 8, 16}; std::list<std::string> fruits{"orange", "apple", "raspberry"}; std::list<char> empty; // Print list. std::for_each(nums.begin(), nums.end(), [](const int n) { std::cout << n << ' '; }); std::cout << '\n'; // Sums all integers in the list 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 list fruits, checking if there is any. if (!fruits.empty()) std::cout << "First fruit: " << *fruits.begin() << '\n'; if (empty.begin() == empty.end()) std::cout << "list 'empty' is indeed empty.\n"; }
輸出
1 2 4 8 16 Sum of nums: 31 First fruit: orange list 'empty' is indeed empty.
[編輯] 參閱
(C++11) |
返回指向末尾的迭代器 (public member function) |
(C++11)(C++14) |
返回指向容器或陣列開頭的迭代器 (function template) |