Write a c++ function to find a node at a given index and sum the values of its parent and child nodes. Start indexing at 0. The node at index will always have at least one node before it and one node after it. Your function should return the sum of the parent and child node.

int SumBeforeAndAfter(node *head, int index);

struct node

{

int value;

node *next;

node *prev;

};

Example: linked list pointed to by head: 4<->7<->8<->22, index = 1

your function should return 12