Constructor for LinkedList to receive an array C++ - c++

Question

Attempting to write a constructor for LinkedList to be initialised with an array of integers.
The program would call linked(array); which will add all the values within the array in to a linkedlist.
LinkedList::LinkedList(int array[])
{
headPtr->setData(array[0]); //setData method stores the integer at position 0 inside headPtr
Node *currentPtr = headPtr;
for (int i = 0; i < array.length(); ++i) //for loop to add the integers to the next node
{
currentPtr->setNext(new Node(array[i])); //creates a new node with the integer value of array position i
}
}
the trouble is the array.length (coming from Java) and I don't think the array length can be obtained this way?

Answer 1

I would suggest you to use iterator idiom, and make the constructor a templated constructor as:
class LinkedList
{
//...
public:
template<typename FwdIterator>
LinkedList(FwdIterator begin, FwdIterator end)
{
for (;begin != end; ++begin)
{
//treat begin as pointer, and *begin as dereferenced object
}
}
//...
};
And then you can use it as:
int arr[] = {1,2,3,4,5,6,7,8,9,10};
LinkedList lnklist(arr, arr+10);
Not only that. If you've std::vector<int>, then you can also use it to construct the linked list, as:
std::vector<int> v;
//..
LinkedList lnklist(v.begin(), v.end());
So using iterator idiom gives you this much power and flexibility. :-)

Answer 2

As Nawaz explained, going with iterator solution is better. But if you want to go with array ( static one though), then compiler can automatically deduce the size for you.
template<size_t size>
LinkedList::LinkedList(int (&array)[size])
{
headPtr->setData(array[0]); //setData method stores the integer at position 0 inside headPtr
Node *currentPtr = headPtr;
for (int i = 0; i < size++i) //for loop to add the integers to the next node
{
currentPtr->setNext(new Node(array[i])); //creates a new node with the integer value of array position i
}
}
Can be called as shown below.
int arr[] = {1,2,3,4,5,6,7,8,9,10};
LinkedList lnklist(arr);

Answer 3

Like others have said, it is not only important but vital that you get a good introductory C++ book and read it from front to back, simultaneously trying to forget what you know about Java while in C++ mode. They are not remotely similar.
Now to your problem, it can be solved by using std::vector and using its size method:
// put this with the other includes for your file
#include <vector>
LinkedList::LinkedList(const std::vector<int>& array)
{
headPtr->setData(array[0]); //setData method stores the integer at position 0 inside headPtr
Node *currentPtr = headPtr;
for (int i = 0; i < array.size(); ++i) //for loop to add the integers to the next node
{
currentPtr->setNext(new Node(array[i])); //creates a new node with the integer value of array position i
}
}
If you don't want to use vector, you have to pass in the size of the array to the function:
LinkedList::LinkedList(int array[], int arrlen)
{
headPtr->setData(array[0]); //setData method stores the integer at position 0 inside headPtr
Node *currentPtr = headPtr;
for (int i = 0; i < arrlen; ++i) //for loop to add the integers to the next node
{
currentPtr->setNext(new Node(array[i])); //creates a new node with the integer value of array position i
}
}
But it is recommended to use the vector version.