When one list is exhausted the remaining keys come

* When one list is exhausted, the remaining keys come from the other list.
* For example: [1, 2] and [3, 4, 5] would return [1, 3, 2, 4, 5]
*/
Node* interleave(Node* list1, Node* list2){
// ******** WRITE YOUR CODE HERE ********
Node* head = NULL;
Node* curr = head;
while(list1 != NULL && list2 != NULL) {
Node* n1 = new Node;
Node* n2 = new Node;
n1->key = list1->key;
n2->key = list2->key;
n1->next = n2;
n2->next = NULL;
if(head == NULL) {
head = n1;
} else {
curr->next = n1;
}
curr = n2;
list1 = list1->next;
list2 = list2->next;
}
while(list2 != NULL) {
Node* n2 = new Node;
n2->key = list2->key;
n2->next = NULL;
if(head == NULL) {
head = n2;
curr = head;
} else {
curr->next = n2;
curr = curr->next;
}
list2 = list2->next;
}
while(list1 != NULL) {

Node* n1 = new Node;
n1->key = list1->key;
n1->next = NULL;
if(!head) {
head = n1;
curr = head;
} else {
curr->next = n1;
curr = curr->next;
}
list1 = list1->next;
}
return head;
}