leetcode 146. LRU Cache

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.

get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.
set(key, value) - Set or insert the value if the key is not already present. When the cache reached its capacity, it should invalidate the least recently used item before inserting a new item.

class LRUCache{struct Node{int val;int key;Node*pre, *nxt;Node(int x) :val(x){pre = NULL;nxt = NULL;}};int capa;int cursize;Node*head;Node*tail;unordered_map<int, Node*>keymap;public:~LRUCache(){for (unordered_map<int, Node*>::iterator it = keymap.begin(); it != keymap.end(); it++)delete it->second;}LRUCache(int capacity) {capa = capacity;head = NULL;tail = NULL;cursize = 0;}int get(int key) {if (capa > 0){unordered_map<int, Node*>::iterator it = keymap.find(key);if (it == keymap.end())return -1;Node*pre = it->second->pre;Node*nxt = it->second->nxt;if (pre != NULL){if (it->second == tail)tail = pre;pre->nxt = nxt;if (nxt!=NULL)nxt->pre = pre;it->second->nxt = head;head->pre = it->second;it->second->pre = NULL;head = it->second;}return it->second->val;}return -1;}void set(int key, int value) {if (capa > 0){unordered_map<int, Node*>::iterator it = keymap.find(key);if (it == keymap.end()){if (cursize == capa){keymap.erase(keymap.find(tail->key));tail->key = key;tail->val = value;keymap[key] = tail;if (head != tail){Node*pre = tail->pre;pre->nxt = NULL;tail->nxt = head;head->pre = tail;head = tail;head->pre = NULL;tail = pre;}}else{Node*n = new Node(value);n->key = key;if (head == NULL){head = n;tail = n;}else{n->nxt = head;head->pre = n;head = n;}keymap[key] = n;cursize++;}}else{Node*pre = it->second->pre;Node*nxt = it->second->nxt;if (pre != NULL){if (it->second == tail)tail = pre;pre->nxt = nxt;if (nxt != NULL)nxt->pre = pre;it->second->nxt = head;head->pre = it->second;it->second->pre = NULL;head = it->second;}it->second->val = value;}}}};

accept