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linked_list.cpp
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linked_list.cpp
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// pair wise swap
Node *pairwiseSwap(Node *head){
if(head==NULL||head->next==NULL)
return head;
Node *curr=head->next->next;
Node *prev=head;
head=head->next;
head->next=prev;
while(curr!=NULL&&curr->next!=NULL){
prev->next=curr->next;
prev=curr;
Node *next=curr->next->next;
curr->next->next=curr;
curr=next;
}
prev->next=curr;
return head;
}
// LRU CACHE
class Node {
public:
int key;
int value;
Node *pre;
Node *next;
Node(int k, int v)
{
key = k;
value = v;
pre=NULL;next=NULL;
}
};
class LRUCache {
public:
unordered_map<int, Node*> map;
int capacity, count;
Node *head, *tail;
LRUCache(int c)
{
capacity = c;
head = new Node(0, 0);
tail = new Node(0, 0);
head->next = tail;
tail->pre = head;
head->pre = NULL;
tail->next = NULL;
count = 0;
}
void deleteNode(Node *node)
{
node->pre->next = node->next;
node->next->pre = node->pre;
}
void addToHead(Node *node)
{
node->next = head->next;
node->next->pre = node;
node->pre = head;
head->next = node;
}
int get(int key)
{
if (map[key] != NULL) {
Node *node = map[key];
int result = node->value;
deleteNode(node);
addToHead(node);
cout<<"Got the value : " <<
result << " for the key: " << key<<endl;
return result;
}
cout<<"Did not get any value" <<
" for the key: " << key<<endl;
return -1;
}
void set(int key, int value)
{
cout<<"Going to set the (key, "<<
"value) : (" << key << ", " << value << ")"<<endl;
if (map[key] != NULL) {
Node *node = map[key];
node->value = value;
deleteNode(node);
addToHead(node);
}
else {
Node *node = new Node(key, value);
map[key]= node;
if (count < capacity) {
count++;
addToHead(node);
}
else {
map.erase(tail->pre->key);
deleteNode(tail->pre);
addToHead(node);
}
}
}
};