Need help in putting data into an array in c++

[googled123]

Hi guys,
I need to create an array in c++. But before I declare how many elements are in the array I want to prompt the user for input. I want to ask the user how many elements do they want in the array.
What ever the user said, 5 or 20. I then want to enter these 5 values or 20 values myself.
hope you can help.

 

[DrGreg]

Do you know what the new operator is, and how to use it with an array?

 

[Timo]

You may want to consider using the c++ structure "vector" rather than an array. A vector v (of double values in this example) of size N is created by

  // ... determine the value of N here ...

  // create a vector of N double values.
  std::vector<double> v(N);

The usage is the same as for an array (except for extra options that you may find out some day).

 

[jtbell]

I'm guessing this is a class assignment, so you need to use an array instead of a vector. But for future reference...

Going further from Timo's example, you can declare the vector to have zero size initially, and then let it automatically expand as you add data to it. That way, you don't have to ask the user how many numbers he's going to enter.

#include <iostream>
#include <vector>

using namespace std;

int main ()
{
    vector<int> numbers;  // has length zero, initially

    cout << "Enter some numbers, terminating with control-D:" << endl;

    int n;
    while (cin >> n)
    {
        numbers.push_back(n);  // append n to the vector and expand
                               // the vector as necessary
    }

    // the size() member function tells you how big the vector is

    cout << "You entered:" << endl;
    for (int k = 0; k < numbers.size(); ++k)
    {
        cout << numbers[k] << endl;
    }

    return 0;
}

Input/output:

jtbell$ g++ vector_demo.cpp
jtbell$ ./a.out
Enter some numbers, terminating with control-D:
12
23
34
45
[I][COLOR="Blue"](control-D entered here)[/COLOR][/I]
You entered:
12
23
34
45
jtbell$

 

[LudusRex]

Hi there,

Creating an array in C++ is a great way to store and manipulate data. In order to put data into an array, you will first need to declare the array and specify its size. This can be done using the syntax: "data_type array_name [array_size];"

In your case, since you want to prompt the user for the array size, you can use the "cin" function to get user input and store it in a variable. Then, you can use this variable as the size for your array.

Next, you can use a loop to ask the user for input for each element in the array. This can be done using the "cin" function again, and storing the values in the array using the index notation.

For example, if your array is called "myArray", the syntax for storing values in the array would be: "myArray[index] = value;"

I hope this helps you get started with creating an array and putting data into it in C++. If you need further assistance, don't hesitate to reach out. Best of luck with your project!