Arrays

[ek192010]

Hi, guys I needed some help with this program I was told that in order to do the standard deviation I should put my grades in an array so I was wondering is there anyway that I can put the grades that the user inputs in Choice = 1 into Choice = 3 is there anyway to convert them into an array basically I only wanna use the array in Choice = 3 can someone guide me the to the right path Thanks =)

#include <iostream>
#include <math.h>
using namespace std;

void Display_Menu();

int main ()
{
    Display_Menu();

	int choice,grad,count,sum;
	int min = 100;
	int max = 0;
	int average,diff;

	cin >> choice;

    while (choice != 'q')
	{
    if (choice == 1)
		{
			while (grad >= 0)
			{
		     cout <<"Enter the necessary grades.\n";
			 cin >>grad;
			 if (grad >=0)
			 {
				 sum = sum + grad;
				 count++;
			 }
		    if (grad <min && grad > 0)
		    {
			  min = grad;
		    }
			if (grad > max)
		    {
			  max = grad;
			}
			}
		  cout <<"Enter you're next choice.\n";
		  cin >> choice;
	    }
	if (choice == 2)
	{
	  average = sum/count;
	  cout << "This is the average of the grades entered.\n" << average << "\n";
	  cout << "Select you're next choice.\n";
	  cin >> choice;
	}
	if (choice == 3)
	{
	}
	if (choice == 4)
	{
		cout << "This is the highest grade you entered.\n" << max << "\n";
		cout << "This is the lowest grade you entered.\n"  << min << "\n";
	}
	cout << "Goodbye see you next time.\n";
	break;
	}
	system ("pause");
	return 0;
}

	
void Display_Menu()
{
	cout << " Option 1 : Enter grades ( Quit with a negative value)\n";
	cout << " Option 2 : Display the Mean(average) for the grades\n";
	cout << " Option 3 : Display the standard deviation for the grades\n";
	cout << " Option 4 : Display the high and low grades\n";
	cout << " Option 5 : Enter 'q' to quit\n";
	cout << "Enter you're choice (1-5)\n";

[vichu8888]

array can be only created if you know its size. otherwise you have to use dynamic array

[vichu8888]

below is the example for creating an dynamic array using pointers

#include<iostream>
using namespace std;


int *get(int size);
int main()
{
	int *pi;
	
	int size;
	cout<<"Enter the length of an array: ";
	cin>>size;
	cout<<endl;

	

	pi=get(size);

	for(int i=0;i<size;i++)
	{
		cout<<pi[i]<<endl;
	}
	delete pi;
	
	system("pause");
	return 0;
}
int *get(int size)
{
	int *list;
	list=new int[size];

	for(int i=0;i<size;i++)
	{
		cout<<"Enter"<<i+1<<" number: ";
		cin>>list[i];
		cout<<endl;
	}
	return list;

}