[英]C++: How do I insert the objects contained in a vector into a set?
I have a vector of objects and I'm trying to copy each object into a set: 我有一个对象向量,我试图将每个对象复制到一个集合中:
std::set<MinTreeEdge>minTreeOutputSet;
for(std::vector<MinTreeEdge>::iterator it = minTreeOutput.begin(); it != minTreeOutput.begin(); ++it)
minTreeOutputSet.insert(*it);
This gives me an error that some kind of comparison (operator<' in '__x < __y'|) is missing from the call to insert. 这给我一个错误,即在插入调用中缺少某种比较('__x <__y'|中的operator <')。 I've tried
我试过了
minTreeOutputSet.insert(minTreeOutput[it]);
as well, but that this gives me the error that there is no match for operator[]. 同样,但这给了我一个错误,即操作符[]不匹配。
Is inserting objects into a set not allowed? 是否不允许将对象插入集合? How do I properly insert the objects in a vector into a set?
如何将向量中的对象正确插入集合中?
You say: 你说:
This gives me an error that some kind of comparison (operator<' in '__x < __y'|) is missing from the call to insert
这给我一个错误,即插入调用中缺少某种比较('__x <__y'|中的operator <')
Thus, you should define operator<
for MinTreeEdge
or pass in your own comparison callable type as the 2nd template argument for std::set<>
. 因此,您应该为
MinTreeEdge
定义operator<
或将您自己的比较可调用类型作为std::set<>
的第二个模板参数传递。
Here is some sample code for both approaches: 这是这两种方法的一些示例代码:
#include <set>
struct A
{
// approach 1: define operator< for your type
bool operator<( A const& rhs ) const noexcept
{
return x < rhs.x;
}
int x;
};
struct B
{
int x;
};
struct BCompare
{
// approach 2: define a comparison callable
bool operator()( B const& lhs, B const& rhs ) const noexcept
{
return lhs.x < rhs.x;
};
};
int main()
{
std::set<A> sa; // approach 1
std::set<B, BCompare> sb; // approach 2
}
I would suggest approach 1 unless you can't modify the definition of your type. 我建议采用方法1,除非您无法修改类型的定义。
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