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容器 | Containers

std::unordered_set::cbegin

STD:无序[医]SET::BEGIN,STD::无序[医]集::

iterator begin((since C++11)
const_iterator begin() const;(since C++11)
const_iterator cbegin() const;(since C++11)

将迭代器返回到容器的第一个元素。

如果容器为空,则返回的迭代器将等于end()...

参数

%280%29

返回值

第一个元素的迭代器。

例外

noexcept规格:

noexcept

复杂性

常量。

二次

#include <iostream> #include <unordered_set> struct Point { double x, y; }; int main() { Point pts[3] = { {1, 0}, {2, 0}, {3, 0} }; //points is a set containing the addresses of points std::unordered_set<Point *> points = { pts, pts + 1, pts + 2 }; //Change each y-coordinate of (i, 0) from 0 into i^2 and print the point for(auto iter = points.begin( iter != points.end( ++iter){ (*iter)->y = ((*iter)->x) * ((*iter)->x //iter is a pointer-to-Point* std::cout << "(" << (*iter)->x << ", " << (*iter)->y << ") "; } std::cout << '\n'; //Now using the range-based for loop, we increase each y-coordinate by 10 for(Point * i : points) { i->y += 10; std::cout << "(" << i->x << ", " << i->y << ") "; } }

二次

可能的产出:

二次

(3, 9) (1, 1) (2, 4) (3, 19) (1, 11) (2, 14)

二次

另见

end cendreturns an iterator to the end (public member function)

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