Question

I am reading in numbers from a file and then trying to add them to an array. My problem is how do you increase the size of the array? For example I thought might be able to just do:

#include <iostream> using namespace std;  int main() {     double *x;     x = new double[1];     x[0]=5;     x = new double[1];     x[1]=6;     cout << x[0] << "," << x[1] << endl;     return 0; } 

But this obviously just overwrites the value, 5, that I initially set to x[0] and so outputs 0,6. How would I make it so that it would output 5,6?

Please realize that for the example I’ve included I didn’t want to clutter it up with the code reading from a file or code to get numbers from a user. In the actual application I won’t know how big of an array I need at compile time so please don’t tell me to just make an array with two elements and set them equal to 5 and 6 respectively.

Answer 1

You don’t want to work with arrays directly. Consider using a vector, instead. Then, you can call the push_back function to add things to the end, and it will automatically resize the vector for you.

#include <iostream> #include <vector>  int main() {     double value;     std::vector<double> values;      // Read in values     while (std::cin >> value) {         values.push_back(value);     }      // Print them back out     for (std::size_t i(0), len(values.size()); i != len; ++i) {         std::cout << values[i];     } }