如何将矢量转换为集合? [英] How to convert vector to set?

问题描述

我有一个向量，我在其中保存对象.我需要将其转换为设置.我一直在阅读关于集合的内容，但我仍有几个问题:

I have a vector, in which I save objects. I need to convert it to set. I have been reading about sets, but I still have a couple of questions:

• 如何正确初始化呢?老实说，一些教程说像 set<ObjectName> 这样初始化它是可以的.一些东西.其他人说你也需要一个迭代器，比如 set<Iterator, ObjectName>一些东西.

• How to correctly initialize it? Honestly, some tutorials say it is fine to initialize it like set<ObjectName> something. Others say that you need an iterator there too, like set<Iterator, ObjectName> something.

如何正确插入.同样，只写 something.insert(object) 就足够了吗?

How to insert them correctly. Again, is it enough to just write something.insert(object) and that's all?

如何从集合中获取一个特定的对象(例如，一个对象中有一个命名变量，等于ben")?

How to get a specific object (for example, an object which has a named variable in it, which is equal to "ben") from the set?

我必须将向量本身转换为一个集合(也就是我必须使用集合而不是向量).

I have to convert the vector itself to be a set (a.k.a. I have to use a set rather than a vector).

推荐答案

你没有告诉我们太多关于你的对象，但是假设你有一个这样的类:

You haven't told us much about your objects, but suppose you have a class like this:

class Thing
{
public:
  int n;
  double x;
  string name;
};

你想把一些东西放到一个集合中，所以你试试这个:

You want to put some Things into a set, so you try this:

Thing A;
set<Thing> S;
S.insert(A);

这失败了，因为集合是排序的，没有办法对事物进行排序，因为没有办法比较它们中的两个.您必须提供 operator<:

This fails, because sets are sorted, and there's no way to sort Things, because there's no way to compare two of them. You must provide either an operator<:

class Thing
{
public:
  int n;
  double x;
  string name;

  bool operator<(const Thing &Other) const;
};

bool Thing::operator<(const Thing &Other) const
{
  return(Other.n<n);
}

...
set<Thing> S;

或比较函数对象:

class Thing
{
public:
  int n;
  double x;
  string name;
};

struct ltThing
{
  bool operator()(const Thing &T1, const Thing &T2) const
  {
    return(T1.x < T2.x);
  }
};

...
set<Thing, ltThing> S;

要查找名称为ben"的事物，您可以遍历集合，但如果您更具体地告诉我们您想要做什么，这将非常有帮助.

To find the Thing whose name is "ben", you can iterate over the set, but it would really help if you told us more specifically what you want to do.

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