iterator end() noexcept; | (1) | (since C++11) |
const_iterator end() const noexcept; | (2) | (since C++11) |
const_iterator cend() const noexcept; | (3) | (since C++11) |
Returns an iterator to the element following the last element of the unordered_map
.
This element acts as a placeholder; attempting to access it results in undefined behavior.
(none).
Iterator to the element following the last element.
Constant.
#include <cmath> #include <iostream> #include <unordered_map> struct Node { double x, y; }; int main() { Node nodes[3] = {{1, 0}, {2, 0}, {3, 0}}; // mag is a map mapping the address of a Node to its magnitude in the plane std::unordered_map<Node*, double> mag = { { nodes + 0, 1 }, { nodes + 1, 2 }, { nodes + 2, 3 } }; // Change each y-coordinate from 0 to the magnitude for (auto iter = mag.begin(); iter != mag.end(); ++iter) { auto cur = iter->first; // pointer to Node cur->y = mag[cur]; // could also have used cur->y = iter->second; } // Update and print the magnitude of each node for (auto iter = mag.begin(); iter != mag.end(); ++iter) { auto cur = iter->first; mag[cur] = std::hypot(cur->x, cur->y); std::cout << "The magnitude of (" << cur->x << ", " << cur->y << ") is "; std::cout << iter->second << '\n'; } // Repeat the above with the range-based for loop for (auto i : mag) { auto cur = i.first; cur->y = i.second; mag[cur] = std::hypot(cur->x, cur->y); std::cout << "The magnitude of (" << cur->x << ", " << cur->y << ") is "; std::cout << mag[cur] << '\n'; // Note that in contrast to std::cout << iter->second << '\n'; above, // std::cout << i.second << '\n'; will NOT print the updated magnitude } }
Possible output:
(C++11) | returns an iterator to the beginning (public member function) |
(C++11)(C++14) | returns an iterator to the end of a container or array (function template) |
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