array again

[muhammad92]

it's about array again, but in simple coding.
erm, my question is, why always windows always says "has stop working"..??

my array coding does not use any pointer and do not want to use it (alternatif ways as my lecturer say).
can anyone help me?

#include <iostream>

using namespace std;

int main()
{
	int size=0;
	float weight[size];

	std::cout<<"Enter number of students of school schildren : "; 
	std::cin>>size;
	std::cout<<"Enter weight of students for "<<size<<" school schildren : "<<endl<<endl;

   for (int i = 0; i < size; i ++)
		{
      	std::cout<< i + 1 << ": ";
      	std::cin>>weight[i];
   	}

	std::cout << "\nWeights : "<<endl<<endl;
	for (int i = 0; i < size; i ++)
	   {
      	std::cout<< i + 1 << ": " << weight[i]<<endl<<endl;
		}

	system ("PAUSE");
	return 0;
}

[Chervil]

Line 8 requires that size is a constant. To do anything useful, size should be greater than zero.

try lines 7 and 8

    const int size = 50;
    float weight[size];

at line 11, the value input should be no greater than the previously specified size. You will have to use a separate variable for this, as size is a constant.

[muhammad92]

okeyh. but i want user to enter their own array size
have any options?

[S G H]

You should use std::vector then, or use new and delete by yourself.
See here: http://www.cplusplus.com/reference/vector/vector/

[Chervil]

There are several options. One is to make sure the previously defined array is large enough to hold the user input.

Or create a dynamically allocated array, using the new and delete operators.

A std::vector is recommended. The size of a vector can change as required.
http://www.cplusplus.com/reference/vector/vector/

#include <iostream>
#include <vector>

using namespace std;

int main()
{
    int size=0;
    vector <float> weight;

    std::cout<<"Enter number of students of school schildren : ";
    std::cin>>size;
    weight.resize(size);
    std::cout<<"Enter weight of students for "<<size<<" school schildren : "<<endl<<endl;

    for (int i = 0; i < size; i ++)
    {
        std::cout<< i + 1 << ": ";
        std::cin>>weight[i];
    }

    std::cout << "\nWeights : "<<endl<<endl;
    for (int i = 0; i < size; i ++)
    {
        std::cout<< i + 1 << ": " << weight[i]<<endl<<endl;
    }

    system ("PAUSE");
    return 0;
}

Often, the vector size is not specified, but instead is allowed to grow as necessary, like this:

#include <iostream>
#include <vector>

int main()
{
    int size=0;
    std::vector <float> weight;

    std::cout<<"Enter number of students of school schildren : ";
    std::cin>>size;

    std::cout<<"Enter weight of students for "<<size
             <<" school schildren : "<<std::endl<<std::endl;

    for (int i = 0; i < size; i ++)
    {
        std::cout<< i + 1 << ": ";
        float w;
        std::cin >> w;
        weight.push_back(w);
    }

    std::cout << "\nWeights : "<<std::endl<<std::endl;
    for (int i = 0; i < weight.size() ; i ++)
    {
        std::cout<< i + 1 << ": " << weight[i]<<std::endl<<std::endl;
    }

    std::system ("PAUSE");
    return 0;
}

[muhammad92]

i think the problem is solved..

actually, in my course university syllabus, vector and pointer are in semester 2..
i'm now in semester 1...

my lecturer says that we can use array size defined by user without using vector and pointer. but, he doesn't want to teach us how to use the alternatif way.

thus, as conclusion, i only use pointer and vector...

[Chervil]

In standard C++, the size if an array must be a constant known at compile time. If the size is to be chosen by the user, then you should use something like this:
float * weight = new float [size];

and when processing is finished, release the memory with
delete [] weight;

The original method (at the start of this thread) will not compile as standard C++, but some compilers will permit it.