[英]How to use std::sort to sort particular objects from an array?
我有這些類,我想對一個對象數組進行排序,考慮x坐標,並對具有特定值的屬性進行排序。
Class.h
#include <iostream>
#include <algorithm>
class Punct2D
{
protected:
int x, y;
public:
Punct2D() {};
~Punct2D() {};
int get_x() const;
int get_y() const;
void set_x(const int x);
void set_y(const int y);
friend std::ostream &operator << (std::ostream &flux, Punct2D dot);
friend std::istream &operator >> (std::istream &flux, Punct2D &dot);
};
class Punct2DColorat :public Punct2D
{
private:
char *color;
public:
Punct2DColorat() { this->color = NULL; };
~Punct2DColorat() {};
char *get_color();
void set_color(char *color);
bool operator<(Punct2DColorat dot);
};
我在這里實施。
#include "Class.h"
int Punct2D::get_x() const
{
return this->x;
}
int Punct2D::get_y() const
{
return this->y;
}
void Punct2D::set_x(const int x)
{
this->x = x;
}
void Punct2D::set_y(const int y)
{
this->y = y;
}
char *Punct2DColorat::get_color()
{
return this->color;
}
void Punct2DColorat::set_color(char *color)
{
this->color = new char[strlen(color) + 1];
for (int i = 0; i < strlen(color) + 1; i++) this->color[i] = color[i];
}
bool Punct2DColorat::operator<(Punct2DColorat dot)
{
return this->x < dot.get_x();
}
std::ostream &operator << (std::ostream &flux, Punct2D dot)
{
flux << "Punct(" << dot.get_x() << "," << dot.get_y() << ")\n";
return flux;
}
std::istream &operator >> (std::istream &flux, Punct2D &dot)
{
std::cout << "Introduceti x :";
flux >> dot.x;
std::cout << "Introduceti y :";
flux >> dot.y;
return flux;
}
這是主要的。
#include "Class.h"
void main()
{
int n, it = 0; char *aux = new char[15]; bool value;
Punct2DColorat *dots;
std::cout << "Cate puncte introduceti :"; std::cin >> n;
dots = new Punct2DColorat[n];
for (int i = 0; i < n; i++)
{
std::cout << "Introduceti 0 pentru Punct2D, respectiv 1 pentru Punct2D colorat :";
std::cin >> value;
if (value)
{
std::cin >> dots[i];
std::cout << "Introduceti culoarea punctului :";
std::cin >> aux;
dots[i].set_color(aux);
}
else
{
std::cin >> dots[i];
}
}
std::sort(dots, dots + n, [](Punct2DColorat dot) { return dot.get_color() != NULL; });
for (int i = 0; i < n; i++)
{
std::cout << dots[i];
if (dots[i].get_color() != NULL)
{
std::cout << "Culoare :" << dots[i].get_color() << "\n";
}
std::cout << "\n";
}
}
我想用顏色對點進行排序!= NULL,我試過這個,它有效,但我有一個運行時錯誤。
bool Punct2DColorat::operator<(Punct2DColorat dot)
{
if ((this->color != NULL) && (dot.get_color() != NULL))return this->x < dot.get_x();
return true;
}
如何只對具有顏色的對象進行排序!= NULL,其他顏色== NULL的對象保持在同一位置?
這是一個例子:
//If have 3 objects in the following order stored in the dots array.
dots[0].get_x()=3;
dots[0].get_y()=3;
dots[0].get_color()="Red";
dots[1].get_x()=0;
dots[1].get_y()=0;
dots[1].get_color()=NULL;
dots[2].get_x()=1;
dots[2].get_y()=1;
dots[2].get_color()="Blue";
//After sort i want to have them like this:
dots[0].get_x()=1;
dots[0].get_y()=1;
dots[0].get_color()="Blue";
dots[1].get_x()=0;
dots[1].get_y()=0;
dots[1].get_color()=NULL;
dots[2].get_x()=3;
dots[2].get_y()=3;
dots[2].get_color()="Red";
謝謝。
問題是,對於任何幾個非彩色點,您的比較運算符的計算結果為true。 一種可能的解決方案是構造第二個向量,對其進行排序並重新插入
std::vector<Punct2DColorat> tmp;
for (int i = 0; i < n; i++)
{
if (dots[i].get_color() != NULL)
{
tmp.push_back(dots[i]);
}
}
std::sort(tmp.begin(), tmp.end());
int j = 0;
for (int i = 0; i < n; i++)
{
if (dots[i].get_color() != NULL)
{
dots[i] = tmp[j];
++j;
}
}
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