std::unordered_set::cbegin
STD:无序[医]SET::BEGIN,STD::无序[医]集::
iterator begin( | | (since C++11) |
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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。
例
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 cend | returns an iterator to the end (public member function) |
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