Question

I have to allocate in C++ an array of struct, any struct contains two vector of int. This is my struct:

typedef struct _Sample{
vector<int> contourX;
vector<int> contourY;
}Sample;

To allocate this array I write the following code:

data = (struct _Sample*) malloc(sizeof(struct _Sample) * nsamples);

When I try to assign a Sample element to data[0] I have an error a runtime. Where is the problem?

Answer 1

You are trying to create an array, for that, you should use new[] to allocate the memory (and delete [] to deallocate it).

That way your code should be:

Sample* data = new Sample[nsamples];

Then you can iterate over each element of your array like any array:

for(int i = 0; i < nsamples; i++)
{
    data[i].contourY // do something
    data[i].contourX // do something
}