Generic vector sort (C++)
Contents
Description
This example demonstrates how to sort a generic vector in a C++ application. This example uses the Standard Template Library (STL) headers <vector> and <algorithm>.
The example contains three files:
- Shapes.h - Declares classes that describe the following geometric shapes: Triangle, Rectangle, Square.
- Shapes.cpp - Contains the implementation of the classes declared in Shapes.h.
- Main.cpp - Main file; Declares a vector of shapes, adds some shapes to the vector, then sorts the shapes in the vector by their area.
Code
- Main.cpp
#pragma hdrstop
#pragma argsused
#include <tchar.h>
#include <stdio.h>
#include <vector>
#include <algorithm>
#include <iostream>
#include "Shapes.h"
using namespace std;
// prints the area for each element of the vector
void PrintVector(vector<Shape*>vect) {
#ifdef _WIN64
for (auto i = vect.begin(); i < vect.end(); i++) {
#else
for (vector<Shape*>::iterator i = vect.begin(); i != vect.end(); ++i) {
#endif
cout << (*i)->GetArea() << " ";
}
cout << endl;
}
#ifdef _WIN32
// compare function for 32bit applications
bool compareFunction(Shape* left, Shape* right) {
int al = left->GetArea(), ar = right->GetArea();
return (al < ar);
}
#endif
int _tmain(int argc, _TCHAR* argv[]) {
// declare a vector of Shape*
vector<Shape*>v;
// add three different shapes:
// a rectangle, a triangle and a square
v.push_back(new Rectangle(3, 5));
v.push_back(new Triangle(1, 2, 3));
v.push_back(new Square(3));
// print the vector
cout << "Unsorted vector:";
PrintVector(v);
// sort the vector
// the compare function is defined as a lambda expression
#ifdef _WIN64
sort(v.begin(), v.end(), [](Shape * left, Shape * right)->bool
{int al = left->GetArea(), ar = right->GetArea(); return (al < ar);});
#else
sort(v.begin(), v.end(), compareFunction);
#endif
// print the vector again to check if the areas are sorted
cout << "Sorted vector:";
PrintVector(v);
cin.get();
return 0;
}
- Shapes.h:
// ---------------------------------------------------------------------------
#ifndef ShapesH
#define ShapesH
// ---------------------------------------------------------------------------
// base class for shapes
class Shape {
public:
// pure virtual function
// in derived classes, GetArea returns the area of the shape
virtual double GetArea() = 0;
};
// class that describes a triangle shape
class Triangle : public Shape {
private:
// the length of the sides
double x, y, z;
public:
// triangle constructor
Triangle(double x, double y, double z);
// returns the area of the triangle
#ifdef _WIN64
double GetArea() override;
#else
double GetArea();
#endif
};
// class that describes an rectangle shape
class Rectangle : public Shape {
private:
// the length of the sides
double lg, lat;
public:
// rectangle constructor
Rectangle(double lg, double lat);
// returns the area of the rectangle
#ifdef _WIN64
double GetArea() override;
#else
double GetArea();
#endif
};
// class that describes an square shape
class Square : public Rectangle {
public:
// square constructor
// calls the rectangle shape constructor having the lengths of the two different sides the same
Square(double lat) : Rectangle(lat, lat) {
}
};
#endif
- Shapes.cpp
#pragma hdrstop
#include "Shapes.h"
#include <math.h>
// Triangle constructor
Triangle::Triangle(double x, double y, double z) {
this->x = x;
this->y = y;
this->z = z;
}
// returns the triangle area
// uses Heron's formula
double Triangle::GetArea() {
double s = (x + y + z) / 2;
return sqrt(s*(s - x)*(s - y)*(s - z));
}
// Rectangle constructor
Rectangle::Rectangle(double lg, double lat) {
this->lg = lg;
this->lat = lat;
}
// returns the rectangle area
double Rectangle::GetArea() {
return (lg * lat);
}
#pragma package(smart_init)
Uses
- Modern C++ Features Supported by RAD Studio Clang-enhanced C++ Compilers
- Standard Template Library (STL)