Adding integers per line and storing it in array - c++

Question

I'm trying to create a mini function using dynamically allocated arrays instead of vectors because I'm trying to figure out how they work exactly.
So basically, the user enters how many number of lines they want, and then after that, they enter in a group of integers/doubles separated by a space. Then, I want the function to calculate the total sum of integers in each line, allocate it into the array.
For example:
3
1 2 3 4
3 2 2 1 //assume each line has the same # of integers (4)
1 4 4 1
Then, if I implemented my function the total of sum would then be 10, 8, 10.
So far, I have this:
int* total //is there a difference if I do int *total ??
int lines;
std::cout << "How many lines?;
std::cin >> lines;
total = new int[lines];
for (int i=0;i<lines;i++)
{
for (int j=0;j<4;j++)
{
total[i] = ? //i'm confused how you add up each line and then put it in the array, then go onto the next array..
}
}
If anything does not make sense, please feel free to ask! Thank you!

Answer 1

you probably will want to set total[i] to 0 right before the inner loop, and then just use operator+= to add anything you get from the std::cin stream.
// ...
total[i]=0;
for (int j=0;j<4;j++)
{
int temp;
cin >> temp;
total[i] += temp;
}
// ...
It could be a bit easier to understand if you first allocated an array to store the values and then added them together.

Answer 2

First of all you need to allocate an array of arrays to store numbers of each line. For example
const size_t COLS = 4;
size_t rows;
std::cout << "How many lines? ";
std::cin >> rows;
int **number = new int *[rows];
for ( size_t i = 0; i < rows; i++ )
{
number[i] = new int[COLS];
}
int *total = new int[rows];
// or int *total = new int[rows] {}; that do not use algorithm std::fill
std::fill( total, total + rows, 0 );
After that you should enter numbers and fill each row of number.

Answer 3

There really isn't any difference between doing int* total and int *total (in your example anyways). Personally, I prefer the second one.
As for your question, you would need to set your total to an initial value (in this case you would set it to zero) and then from there just add onto it after getting the value from cin.
With cin, since you have the spaces, it will get each individual number (as you know, I'm assuming) however you probably should (I would) store that number into another variable and then add that variable onto the total for that row.
I think that all makes sense. Hope it helps.

Answer 4

IMHO you can do it using a 2 dimensional array:
int** total;
// ...
total = new int*[lines];
for(int i = 0; i < lines; ++i)
{
total[i] = new int[4]; // using magic number is not good, but who cares?
for(int j = 0; j < 4; ++j)
{
int tmp;
std::cin>>tmp;
total[i][j] = tmp;
}
}
// do sth on total
for(int i = 0; i < lines; ++i)
delete[] total[i];
delete[] total;