int SkipList::add(const Key& key, bool verbose) {
if (find(key, false) != 0) {
if (verbose) {
cout<<"Node "<<key<<" is already in the list."<<endl;
}
return 0;
}
SkipListNode* newNode = new SkipListNode(key, randHeight());
if (verbose) {
cout<<"Add new node "<<*newNode<<" with height "<<newNode->height()<<endl;
}
int ret = add (m_head, newNode, m_maxHeight-1);
if (ret == 0 ) {
return ret;
}
return 1;
}
/////////////////////////////////////////////////////////////
///////////////////// DEL FUNCTION ////////////////////////
/////////////////////////////////////////////////////////////
SkipListNode* SkipList::del(SkipListNode* target, const Key& key,
unsigned level) {
if (target->nextAtLevel(level) != NULL &&
*target->nextAtLevel(level) < key) {
countDelete++;
}
////////////// Write your code below ////////////////////////
// deleting from an empty skip list returns null
if (target == NULL) return NULL;
SkipListNode * t = target->nextAtLevel(level);
// if hits the end of the current level, goes down the level
if (t == NULL) {
// if level is already 0, key is not found
if (level == 0) return NULL;
return del(target, key, level-1);
}
// node is found
if (*t == key) {
target->setNextAtLevel(level, t->nextAtLevel(level));
if (level == 0) return t;
// if level is > 0, recurssively delete its corresponding node at lower levels
return del(target, key, level-1);
}
// if the key is smaller than the node, means it can't be located after the node
// go down the level to find it
if (key < *t) {
return del(target, key, level-1);
}
// if the key is larger than the node, keep checking in the same level
return del(t, key, level);
}
void SkipList::dump(char sep) {
int length = -1;
cout << "Current List: ";
for (SkipListNode* iter = m_head; iter != NULL; iter = iter->nextAtLevel(0)) {
length++;
cout << string(*iter) << " ";
cout << "(" << iter->height() << ":";
for (unsigned i = 0; i < iter->height(); i++) {
if (iter->nextAtLevel(i)) {
cout << " "<< i << ":" << *(iter->nextAtLevel(i));
cout.flush();
}
}
cout << ")" << sep;
}
cout << length << " nodes in total." << endl;
}
