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146LRUCache.java
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146LRUCache.java
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class DLinkedNode {
DLinkedNode pre;
DLinkedNode next;
int val;
int key;
public DLinkedNode(int key, int val) {
this.pre = null;
this.next = null;
this.val = val;
this.key = key;
}
}
private HashMap<Integer, DLinkedNode> map;
int capacity;
int count;
DLinkedNode head, tail;
public LRUCache(int capacity) {
this.capacity = capacity;
this.count = 0;
this.map = new HashMap<Integer, DLinkedNode>();
this.head = new DLinkedNode(-1, -1);
this.tail = new DLinkedNode(-1, -1);
this.head.next = this.tail;
this.tail.pre = this.head;
}
public int get(int key) {
DLinkedNode cur = map.get(key);
if (cur == null) return -1;
moveToHead(cur);
return cur.val;
}
public void set(int key, int value) {
DLinkedNode cur = map.get(key);
if (cur == null) {
cur = new DLinkedNode(key, value);
this.map.put(key, cur);
addNode(cur);
count++;
if (count > this.capacity) {
DLinkedNode popTail = removeTail(); // important
this.map.remove(popTail.key);
count--;
}
}
else {
map.get(key).val = value;
moveToHead(map.get(key));
}
}
private void addNode(DLinkedNode node) {
DLinkedNode next = head.next;
node.pre = head;
node.next = next;
next.pre = node;
head.next = node;
}
private void moveToHead(DLinkedNode node) {
removeNode(node);
addNode(node);
}
private void removeNode(DLinkedNode node) {
DLinkedNode pre = node.pre;
DLinkedNode next = node.next;
pre.next = next;
next.pre = pre;
}
private DLinkedNode removeTail() {
DLinkedNode cur = tail.pre;
removeNode(cur);
return cur;
}
public class LRUCache {
private final int capacity;
private int curCapacity = 0;
private CacheNode head;
private CacheNode tail;
private HashMap<Object, CacheNode> map;
private class CacheNode {
CacheNode prev;
CacheNode next;
int val;
int key;
public CacheNode(int k, int v) {
val = v;
key = k;
}
}
public LRUCache(int capacity) {
this.capacity = capacity;
curCapacity = 0;
map = new HashMap<Object, CacheNode>(capacity);
}
public int get(int key) {
CacheNode cur = map.get(key);
if(cur == null) return -1;
else {
move(cur);
return cur.val;
}
}
public void set(int key, int value) {
CacheNode node = map.get(key);
if(node == null) {
node = new CacheNode(key, value);
if(curCapacity < capacity) curCapacity++;
else if(tail != null){
map.remove(tail.key);
removeTail();
}
move(node);
map.put(key, node);
}
else {
node.val = value;
move(node);
map.put(key, node);
}
}
private void move(CacheNode node) {
if(node == null || node == head) return;
if(head == null || tail == null) {
head = node;
tail = node;
return;
}
if(node == tail) tail = tail.prev;
if(node.prev != null) node.prev.next = node.next;
if(node.next != null) node.next.prev = node.prev;
node.next = head;
node.prev = null;
head.prev = node;
head = node;
}
private void removeTail() {
if(tail != null) {
if(tail.prev != null) {
tail.prev.next = null;
}
else {
head = null;
}
tail = tail.prev;
}
}
}