如何删除向量类型的重复项 <string> 在C ++中？

Question

I know that a good way to prevent duplicates is to use an unordered_set . However, this method does not seem to work when I want to have an unordered_set<vector<string>> . How can I go about doing this? For example, I want to prevent <"a", "b", "c"> from being duplicated in my unordered_set<vector<string>> .

Can this unordered_set<vector<string>> be used outside the defined class as well?

Code:

unordered_set<vector<string>> abc({"apple", "ball", "carrot"});
abc.insert({"apple", "ball", "carrot"});

cout << abc.size() << endl;     //abc.size() should be 1

Answer 1

There is a number of ways to get rid of duplicates, building a set out of your objects is one of them. Whether it is going to be std::set or std::unordered_set is up to you to decide, and the decision usually depends on how good of a hash fuction can you come up with.

This in turn requires the knowledge of the domain, eg what your vectors of strings represent and what values can they have. if you do come up with a good hash, you can implement it like this:

struct MyHash
{
    std::size_t operator()(std::vector<std::string> const& v) const 
    {
        // your hash code here
        return 0; // return your hash value instead of 0
    }
};

Then you just declare your unordered_set with that hash:

std::unordered_set<std::vector<std::string>, MyHash> abc;

I would say it's a safe bet to just go with a std::set at first though, unless you have a good hash function on your mind.