C++ selection sort - insert method and private variables

Question

I'm in the process of writing a program for selection sort. I just posted something regarding std::vector, however this post is on a different subject.

I was able to compile the program, however it was running into run-time error when insert() was invoked in the main method.

My ArrayS has the code below as a copy constructor and also to initialize nElems to 0 when ArrayS is created.

[ArrayS.cpp]

ArrayS::ArrayS(int max)
{
    std::vector<long> a;                 
    nElems = 0; 
}

void ArrayS::insert(long value)    // put element into array
      {
      a[nElems] = value;             // insert it
      nElems++;                      // increment size
      }

[ArrayS.h]

private:

std::vector<long> a;

int nElems; 

Now, do I need get/set method in the ArrayS.cpp to manipulate nElems? I'm not sure how in C++ you work with private variables.

Thank you.

Answer 1

Vectors keep track of their size. And to be efficient, a[nElems] will assume that your vector is large enough to accommodate that access.

It looks like you want:

void ArrayS::insert(long value)    // put element into array
      {
      a.push_back(value);             // insert it AND increment size
      }

It also looks like you can disregard nElems. If you want the vector's size, just call a.size().