打印出在堆上声明的数组时为零。 C++

Question

I want to make a program that lets the user insert some numbers to the array and the print it out afterwards. Problem is when I try to do that (lets say the size of my array is 100) then: What it should do: Inserted- 1,2,3,4,5 -> should print 1,2,3,4,5 But instead it prints -> 1,2,3,4,5,0,0,0,0,0,0, .... up to the size of my array. Is there any way I can get rid of those zeros? Code:

int SIZE = 100;
int main()
{
int *numbers;
numbers = new int[SIZE];
int numOfElements = 0;
int i = 0;
cout << "Insert some numbers (! to end): ";
while((numbers[i] != '!') && (i < SIZE)){
    cin >> numbers[i];
    numOfElements++;
    i++;
}
for(int i = 0; i < numOfElements; i++){
    cout << numbers[i] << " ";
}
delete [] numbers;
return 0;
}

Answer 1

Get numOfElements entered from user beforehand. For example

int main() {
    int n;
    cin >> n;
    int * a = new int[n];
    for (int i = 0; i < n; ++i)
        cin >> a[i];
    for (int i = 0; i < n; ++i)
        cout << a[i] << endl;
    delete[] a;
}

Input

4
10 20 30 40

Output

10 20 30 40

Answer 2

You increase numOfElements no matter what the user types. Simply do this instead:

if(isdigit(numbers[i]))
{
  numOfElements++;
}

This will count digits, not characters. It may of course still be too crude if you want the user to input numbers with multiple digits.

Answer 3

Since you declared array size, all indices will be zeros. User input changes only the first x indices from zero to the value entered (left to right). All other indices remains 0. If you want to output only integers different from 0 (user input) you can do something like that:

for(auto x : numbers){
if(x!=0)cout<<x<<" ";
}

You can use vector and push_back the values from user input to get exactly the size you need without zeros, then you can use this simple code:

for(auto x : vectorName)cout<<x<<" ";

Answer 4

Previous solutions using a counter is fine. otherwise you can (in a while... or similar)

1. read values in a "temp" var
2. add if temp non zero
3. exit loop if counter >= SIZE-1 (you reach max slots)
4. increment counter

when You will print, form 0 to counter, you will get only non zero values.