具有自定义字符串比较器的字符串的priority_queue的C ++向量

问题描述

我有一个 vector 的 priority_queue s是 string s:

I have a vector of priority_queues of strings:

vector<priority_queue<string>>> queues(VECTOR_CAPACITY);

问题是我如何将自定义 string 比较器应用于那些 priority_queue s?

And the question is how can I apply custom string comparator to those priority_queues?

这是否有意义，我想要的比较器将较短的字符串放在较长的字符串之前，并且当它们相等的长度时使用标准字符串比较.

Should this be relevant, the comparator I want puts shorter strings before longer ones and when they're equal length uses standard strings comparison.

我尝试过这种方式:

auto comparator = [] (string s1, string s2) { return s1.length() < s2.length() || s1 < s2; };
vector<priority_queue<string, vector<string>, decltype(comparator)>> queues(VECTOR_CAPACITY);

但它不会编译并显示以下错误:

but it doesn't compile with the following error:

No matching constructor for initialization of 'value_compare' (aka
'(lambda at Example.cpp:202:23)')

---

比较器将较短的字符串放在较长的字符串之前，并且当它们相等的长度时，使用标准的字典比较方法如下:

---

Comparator that puts shorter strings before longer ones and when they're equal length uses standard lexicographic comparison looks like that:

auto comparator = [] (string s1, string s2)
{
    if (s1.length() != s2.length())
    {
        return s1.length() > s2.length();
    }
    return s1.compare(s2) > 0;
};

推荐答案

您还需要将您的lambda实例传递给 std :: priority_queue ，如说:

You also need to pass the instance of your lambda to the std::priority_queue, as this Q&A says:

using my_queue_t = std::priority_queue<
    std::string, std::vector<std::string>, decltype(comparator)>;

std::vector<myqueue_t> queues(VECTOR_SIZE, my_queue_t(comparator));

不幸的是，复制列表初始化即 {comparator} 在这里不起作用，因为第二个构造函数重载由于某种原因被标记为 explicit .

Unfortunately, copy-list-initialization i.e. {comparator} doesn't work here, because the 2nd constructor overload is marked explicit for some reason.

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