Need help solving memory leak error - c++

Question

When I run valgrind, I get one error at method insert for operator new;
I know this probably means that I have to delete node n how I tried so many things to try to delete it but it just gives me even more errors. Please hel.
class key_value_sequences {
public:
struct node{
int key;
vector<int> values;
node* next;
node* prev;
};
key_value_sequences() {
}
~key_value_sequences() {
}
key_value_sequences(const key_value_sequences& A) {
n = A.n;
head = A.head;
tail = A.tail;
v = A.v;
}
key_value_sequences& operator=(const key_value_sequences& A) {
if (this == &A) return *this;
n = A.n;
head = A.head;
tail = A.tail;
v = A.v;
return *this;
}
// YOU SHOULD USE C++ CONTAINERS TO AVOID RAW POINTERS
// IF YOU DECIDE TO USE POINTERS, MAKE SURE THAT YOU MANAGE MEMORY PROPERLY
// IMPLEMENT ME: SHOULD RETURN SIZE OF A SEQUENCE FOR GIVEN KEY
// IF NO SEQUENCE EXISTS FOR A GIVEN KEY RETURN -1
int size(int key) const {
if (find(v.begin(), v.end(), key)!=v.end()) {
node* temp = head;
while(temp != NULL) {
if (temp->key == key) {
return temp->values.size();
}
else temp = temp->next;
}
}
else return -1;
}
// IMPLEMENT ME: SHOULD RETURN POINTER TO A SEQUENCE FOR GIVEN KEY
// IF NO SEQUENCE EXISTS FOR A GIVEN KEY RETURN nullptr
const int* data(int key) const {
if (find(v.begin(), v.end(), key)!=v.end()) {
node* temp = head;
while(temp != NULL) {
if (temp->key == key) {
return temp->values.data();
}
else temp = temp->next;
}
}
else return nullptr;
}
// IMPLEMENT ME: INSERT VALUE INTO A SEQUENCE IDENTIFIED BY GIVEN KEY
void insert(int key, int value) {
if(v.size() == 0) { //empty list
v.push_back(key);
n = new node;
n->prev = NULL;
n->key = key;
n->values.push_back(value);
head = n;
tail = n;
}
else if((find(v.begin(), v.end(), key)!=v.end())) { //if key exists already
node* temp = head;
while(temp != NULL) {
if (temp->key == key) {
temp->values.push_back(value);
break;
}
else temp = temp->next;
}
}
else { //if theres no existing key
v.push_back(key);
n = new node;
n->key = key;
n->values.push_back(value);
n->prev = tail;
tail->next = n;
tail = n;
tail->next = NULL;
}
}
private:
vector<int> v;
node* n;
node* head;
node* tail;
}; // class key_value_sequences
#endif // A3_HPP

Answer 1

In insert method:
if(v.size() == 0) { //empty list
v.push_back(key);
n = new node;
n->prev = NULL;
n->key = key;
n->values.push_back(value);
head = n;
tail = n;
}
You are not setting the head->next to NULL. I suspect that could be the problem while inserting second value.
while(temp != NULL) { // <<<<< Is temp uninitialized?
if (temp->key == key) {
temp->values.push_back(value);
break;
}
else temp = temp->next;
Its pretty dangerous to not initialize the pointer to NULL