Assume the following declarations for a linked list of integers.

class LinkedList $\{$

Node$*$ head;

public:

LinkedList$()\{$

head $=$ NULL;

$\}$

void insert$($int d$)\{$

Node$*$ temp $=$ new Node;

temp$->$data $=$ d;

temp$->$next $=$ head;

head $=$ temp;

$\}$

int getSum$()\{...\}$

$\}$;

Write the member function getSum$()$ that returns the sum of all integers in the linked list.

Thus the following code will print $6$:

LinkedList list;

list.insert$(1)$;

list.insert$(2)$;

list.insert$(3)$;

cout $<<$ list.getSum$()$; $//$prints $6$