How to Make Function using OOP - c++

Question

Anyone can help me to make function using OOP? How to be able to make the function of finding the average of height of students with OOP?
class Person
{
//data members
private:
string name;
int age;
int height;
float weight;
//member functions
public:
void setPerson(string n, int a, int h, float w)
{
name=n;
age=a;
height=h;
weight=w;
}
void setName(string n) { name=n; }
void setAge(int a) { age=a; }
void setHeight(int h) { height=h; }
void setWeight(int w) { weight=w; }
string getName() {return name;}
int getAge() {return age;}
int getHeight() {return height;}
float getWeight() {return weight;}
};
int main()
{
Person p[100];
int x;
cin >> x;
string name;
int age;
int height;
float weight;
for(int i=0; i<x; i++)
{
cin >> name >> age >> height >> weight;
p[i].setName(name);
p[i].setAge(age);
p[i].setHeight(height);
p[i].setWeight(weight);
}
..............
my input are :
3 (number of person)
jason 20 185 70.50 (name age height weight)
emma 19 165 55.55
yerry 25 164 65.10
output :
171.33

Answer 1

Once you have your Persons recorded, it's just a matter of calculating the average height. It should not be a member function of Person, as the class is intended to represent a single Person. An average height is not a property or action taken on/by/to a single Person, so we just calculate it in main().
I've noted changes that I made to your code.
#include <algorithm>
#include <iomanip>
#include <iostream>
#include <string>
#include <vector>
class Person {
// data members
private:
std::string name;
int age;
int height;
float weight;
// member functions
public:
// CHANGE: Change function to constructor
Person(std::string n, int a, int h, float w)
: name(n), age(a), height(h), weight(w) {}
void setName(std::string n) { name = n; }
void setAge(int a) { age = a; }
void setHeight(int h) { height = h; }
void setWeight(int w) { weight = w; }
std::string getName() { return name; }
int getAge() { return age; }
int getHeight() { return height; }
float getWeight() { return weight; }
};
int main() {
std::vector<Person> p; // CHANGE: Switch from C-array to std::vector
int x;
std::cin >> x;
std::string name;
int age;
int height;
float weight;
for (int i = 0; i < x; i++) {
std::cin >> name >> age >> height >> weight;
p.emplace_back(name, age, height,
weight); // CHANGE: Take advantage of vector functionality
// to build Person directly into vector
}
// ADDITION: Calculating average height, std::for_each is subjective here,
// this could have easily been a range-based for loop.
double avgHeight = 0.0;
std::for_each(p.begin(), p.end(), [&avgHeight, size = p.size()](auto person) {
avgHeight += static_cast<double>(person.getHeight()) / size;
});
std::cout << std::fixed << std::setprecision(2) << avgHeight << '\n';
}
Output:
171.33
std::for_each may look goofy, but it's literally just summing heights and dividing by the number of Persons. Like I noted, it could also just be a range-based for loop. I prefer the range-based for loop in this case; I only have std::for_each() because it was a quicker change from my failed attempts at coercing std::reduce to work.
double avgHeight = 0.0;
for (auto i : p) {
avgHeight += static_cast<double>(i.getHeight()) / p.size();
}
The type of i would be better specified as const auto&, but your getters are not marked as const.

Answer 2

You could add a parent struct for Person (call it Individual or something) that has a vector pointer as a member variable. For example, std::shared_ptr<std::vector<double> > Students ( new std::vector<double>() ); The struct would have all the public functions that Person has as pure virtual functions.
Then, add a new void function to Person that derefs Students, and pushes back the height of a new student. Next, you add another function (returning a double or float) that loops through Students to take the sum of the students' heights, and divides it by the size() of the vector.
All Person objects will have pointers to a single Students vector, so every time you push back the height of a new student, it will go to the same place.