使用我自己的函数进行C ++向量排序 [英] C++ vector sorting with my own Function

问题描述

Info:
Parent Class: Vehicle
Child Class : Car & Lorry

我有一个向量，我试图按升序对它进行排序

I got a vector and i trying to sort it by ascending area

sort(myVector.begin()，myVector.end()，compareByArea);

sort(myVector.begin(),myVector.end(),compareByArea);

所以在Vehicle.h

so at the Vehicle.h

我做了

class VehicleTwoD
{
private:
//some variable
public:
bool compareByArea(const VehicleTwoD,const VehicleTwoD);
}

在Vehicle.cpp我做到了

and at Vehicle.cpp i did this

bool VehicleTwoD::compareByArea(const VehicleTwoD &a,const VehicleTwoD &b)
{
return a.getArea() < b.getArea();
}

错误是VehicleTwoD没有名为getArea的成员.

Error was VehicleTwoD has no member named getArea.

它位于我的孩子Car&货车和双人区也在孩子中宣告.

It is located in my child Car & Lorry and double area is also declare in the child .

但是问题是，如果我想通过这种方式进行排序，可以通过使用virtual来实现它，然后在child上创建相同的方法，但是将其重载并以此方式对我的区域进行排序

But the issue is if i want to sort by this way, could i achieve it by using virtual and then I create the same method at child but overload it and get my area sort by that way

有更好的方法吗?

感谢所有帮助！

Additional Info:

我在Car&货车，这只是一个简单的

I have this getArea() function at Car & Lorry which is just a simple

double Car::getArea()
{ return area;}

double Lorry::getArea()
{ return area;}

但是现在当我在向量中得到一个对象列表时，它们每个都是不同类的孩子.但是所有的都有getArea函数，我想对这个向量进行排序

But now as i got a list of object in my vector, each of them is a child of different class. but all got getArea function, i want to sort this vector which is

sortVector.assign(vehicletwod, vehicletwod + arrayCounter);
sort(sortVector.begin(),sortVector.end(),compareArea);

//但排序不起作用.

我不知道在哪里创建compareArea，它可以针对对象2获得对象1的getArea()并返回布尔结果；

I don't know where to create compareArea which can getArea() of object 1 against object 2 and return bool result;

我尝试使用此工具在VehicleTwoD中创建

I try to create it in VehicleTwoD using this

bool VehicleTwoD::compareByArea(const VehicleTwoD &a,const VehicleTwoD &b)
{
return a.getArea() < b.getArea();
}

但是问题是VehicleTwoD没有功能getArea，它们位于子对象上.我应该如何获得此修复程序.谢谢.

But the issue is VehicleTwoD don't have the function getArea, they are located at child. how should i get this fix . Thanks..

感谢帮助:

我尝试了以下

template<typename T> bool compareByArea(const T &a, const T &b) {
    return a.getArea() < b.getArea();
}

我也在.h文件中声明了它，

and i declare it at the .h file too,

public:
template<typename T>
bool compareByArea(const T,const T);
virtual double getArea();

然后在我尝试的main.cpp中

then at my main.cpp i tried

sortVector.assign(vehicletwod, vehicletwod + arrayCounter);
sort(sortVector.begin(),sortVector.end(),sortVector[0].compareArea);

它给我一个错误

sortVector.std :: vector中的成员compareByArea的错误请求< _TP，_ALLOC .......属于非类类型'VehicleTwoD *'

error request for member compareByArea in sortVector.std::vector<_TP, _ALLOC ....... which is of non class type 'VehicleTwoD*'

如果我这样做

  sortVector.assign(vehicletwod, vehicletwod + arrayCounter);
  sort(sortVector.begin(),sortVector.end(),sortVector[0].compareArea);

在此范围内，未声明compareByArea会导致错误.

I will get error compareByArea was not declared in this scope.

我该怎么办?我在main.cpp

What should i do? I declared compareByArea at VehicleTwoD which is included in main.cpp

VehicleTwoD是父类，并且我还虚拟化了double getArea()，因此当它调用getArea时，它将使用子getArea代替，因为私有变量-区域位于子区域，而函数getArea()返回区域也位于孩子

VehicleTwoD is the parent class, and i also virtual double getArea() so when it call getArea it will use the child getArea instead, because the private variable - area is at child and the function getArea() return area is also at child

我该怎么办..困惑&卡住.谢谢！

再次进行最新更新:

我正在尝试通过compareByArea对向量进行排序，其中较小的区域将被排序为最高，而较大的区域将被排序为底部.

I am trying to sort the vector by compareByArea which the smaller area will be sort at the highest while the bigger 1 will be at bottom.

问题是getArea是Car& Car的功能.Lorry(子类)，我在main.cpp中创建了compareByArea

The problem is getArea is a function of Car & Lorry (child class) and i create this compareByArea at main.cpp

sortVector是vehicletwod的向量副本

sortVector is a vector copy of vehicletwod

我将价值设置到我的vehicletwod的方法是这种方式.

The way i set value into my vehicletwod is this way..

if(vehicleType=="Car")
{
vehicletwod[arrayCount] = new Car();
vehicletwod[arrayCount].setDimension();
//set area
vehicletwod[arrayCount].setArea();
cout << "Done setting the data";
}

如何实现按面积递增的排序.

How do i achieve my sorting by area ascending.

我在main.cpp中创建了此功能

I created this function at main.cpp

template<typename T> bool compareByArea(const T &a, const T &b) {
    return a.getArea() < b.getArea();
}

然后我做到了

sortVector.assign(vehicletwod, vehicletwod + arrayCounter);
sort(sortVector.begin(),sortVector.end(),compareByArea);

编译错误:编译错误:

no matching function for call to 'sort(std::vector<VehicleTwoD*>::iterator, std::vector<VehicleTwoD*>::iterator, <unresolved overloaded function type>)'

note: template<class _RAIter> void std::sort (_RAIter, _RAIter)
note: template<class _RAIter, class _Compare> void std::sort(_RAiter, _RAIter, _Compare)

谢谢

我遇到了一个新的编译错误

I got a new compile error

error: passing 'const VehicleTwoD' as 'this' argument of 'virtual double VehicleTwoD::getArea()' discards qualifers.
error: passing 'const VehicleTwoD' as 'this' argument of 'virtual double VehicleTwoD::getArea()' discards qualifers.

关于我的getArea是这个

Regarding my getArea is this

//在父母中是这种方式

//in parent is this way

double VehicleTwoD::getArea()
{
double area;
area=0.00;
return area;
}

汽车-孩子是

 double Car::getArea()
    {
    return area;
    }

推荐答案

启用模板功能:

template<typename T> bool compareByArea(const T *a, const T *b) {
    return a->getArea() < b->getArea();
}

然后您可以将其传递给排序:

then you can pass it to sort:

sort(sortVector.begin(), sortVector.end(), compareByArea<VehicleTwoD>);

更新:

Vehicle.h:

Vehicle.h:

class VehicleTwoD {
...
public:
    virtual double getArea() const;
};

template<typename T> bool compareByArea(const T *a, const T *b) {
    return a->getArea() < b->getArea();
}

main.cpp:

#include "Vehicle.h"
#include <vector>
...
std::vector<VehicleTwoD*> sortVector;
// fill sortVector
sort(sortVector.begin(), sortVector.end(), compareByArea<VehicleTwoD>);
...

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