Question in C++ how can I input infinitely many number without having to cite them in the begining?

Question

Hello I'm new in C++. I'm creating a program to calculate determinants of matrices but I'm having a problem:
when I want to declare a variable so I can give it a value later I start with int a; for an example, but what should I do if I have so many variables it's impossible to write int for every single one of them! thank you.

Answer 1

If you have a large but fixed number of entries then you can use an array as detailed by others.



If you want to be able to cope with a completely arbitrary number of entries limited only by the available memory on the computer then you need to use some form of dynamic memory allocation.

Fortunately c++ makes this fairly easy using the standard container library, for what you want a vector is probably the best option.





#include

using std::vector



main {



// define myIntVector as being a vector of int's, it could be floats, doubles, pointers,

// of a class you have defined or even a vector of vectors if you wanted.



vector myIntVector;





// reserve space for 100 entries. Never needed, it will add space as required but it's

// faster to allocate the space in large blocks if you know you're going to need it.



myIntVector.resize(100);





// add an arbitary number of values

while (more values to add) {

myIntVector.pushBack(newValue);

}



int numberOfEntries = myIntVector.size();

int valueAtLocationSix = myIntVector.at(6); // myIntVector[6] would also work.



myIntVector.clear(); // delete them all

}





See http://www.cplusplus.com/reference/stl/vector/ for more things you can do.

Answer 2

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Answer 3

That is what arrays and dynamic memory are for.

Answer 4

use arrays

int a[10];/* array size of 10 or11 variables it starts from 0 i,e a[0]*/

Answer 5

That's a question for stack overflow

Answer 6

I would suggest to create an array of int then reference each one later. However if you need to add them on as you go a vector would be better rather than having a set number of indexes via an array. This would fix your problem of having a million and a half values. The only other thing is, if you know how many variables you are going to use, then use an array with a fixed amount. If you need more help, feel free to add me and message me as well and I will help as I can.