如何使用自定义比较器对数组排序? [英] How can I sort an array using a custom comparator?

问题描述

当我从下面的代码调用 build 函数时，出现以下编译错误:

When I call my build function from my code below, I get the following compile errors:

error C3867: 'SuffixArray::cmp': function call missing argument list; use '&SuffixArray::cmp' to create a pointer to member
error C2780: 'void std::sort(_RanIt,_RanIt)' : expects 2 arguments - 3 provided

这是我的代码:

class A{
private:
    std::string text;
    std::vector<int> array;

    bool cmp(int a, int b) {
        return std::lexicographical_compare(text.begin() + a, text.end(),
                                            text.begin() + b, text.end());
    }

    void build(const std::string &str, std::vector<int> &vec) {

        // Some vector values actions.

        std::sort(vec.begin(), vec.end(), cmp);
    }
};

这是怎么了?我正在使用Visual C ++编译器.

What's wrong here? I'm using the Visual C++ compiler.

推荐答案

您的比较函数 A :: cmp 是 A 的非静态成员.因此，它需要三个参数:除了显式声明的两个参数之外，它还需要一个指向 A 的指针，以使其成为隐式可用的 this .它也具有与普通函数指针不同的类型: bool(A ::)(int，int)衰减为 bool(A :: *)(int，int)>通过值传递时.

Your comparison function A::cmp is a non-static member of A. Thus, it takes three arguments: in addition to the two arguments explicitly declared, it also takes a pointer to A to become the implicitly available this. It also has a different type than normal function pointers: bool (A::)(int, int) which decays into bool (A::*)(int, int) when being passed by value.

您可以将函数 std :: bind()定位到合适的对象，但是:

You could std::bind() your function to a suitable object, however:

std::sort(vec.begin(), vec.end(),
          std::bind(&A::cmp, this, std::placeholders::_1, std::placeholders::_2));

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