如何遍历 C++ 中的无序集合？
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How does one iterate through an unordered set in C++?
提问by dangerChihuahua007
Suppose I have an unordered set
假设我有一个无序集合
unordered_set<int> my_set;
myset.insert(1);
myset.insert(2);
myset.insert(3);
How do I iterate through it? I don't need to iterate in any order - just as long as I reach each element once. I tried
我如何遍历它？我不需要以任何顺序迭代——只要我到达每个元素一次。我试过
for (int i = 0; i < my_set.size(); i++)
cout << my_set[i];
to no avail.
无济于事。
回答by templatetypedef
You can use the new range-based for loop:
您可以使用新的基于范围的 for 循环：
std::unordered_set<T> mySet;
for (const auto& elem: mySet) {
/* ... process elem ... */
}
Or, you can use the more traditional iterator-based loop:
或者，您可以使用更传统的基于迭代器的循环：
std::unordered_set<T> mySet;
for (auto itr = mySet.begin(); itr != mySet.end(); ++itr) {
/* ... process *itr ... */
}
Or, if you don't have autosupport, perhaps because you don't have C++11 support on your compiler:
或者，如果您没有auto支持，可能是因为您的编译器没有 C++11 支持：
std::unordered_set<T> mySet;
for (std::unordered_set<T>::iterator itr = mySet.begin(); itr != mySet.end(); ++itr) {
/* ... process *itr ... */
}
Hope this helps!
希望这可以帮助！
回答by Kos
Just like any other collection:
就像任何其他集合一样：
for (auto i = my_set.begin(); i != my_set.end(); ++i) {
std::cout << (*i) << std::endl;
}
Or a bit more generic way using overloads of beginand endfunctions (you can write overloads for your own types; they also work on plain arrays):
或者使用begin和end函数重载的更通用的方法（您可以为自己的类型编写重载；它们也适用于普通数组）：
for (auto i = begin(my_set); i != end(my_set); ++i) {
...
}
回答by Mario
Never used them so far, but I'd guess you can use an iterator the same way you do with std::set:
到目前为止从未使用过它们，但我猜你可以像使用 迭代器一样使用迭代器std::set：
for(unordered_set<int>::iterator a = my_set.begin(); a != my_set.end(); ++a) {
int some_int = *a;
}
