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LRUCache.java
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103 lines (87 loc) · 2.26 KB
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package test;
import java.util.HashMap;
import java.util.Map;
public class LRUCache {
private Map<Integer, Node> map;
private DoubleList cache;
private Integer capacity;
public LRUCache(int capacity) {
this.map = new HashMap<>();
this.cache = new DoubleList();
this.capacity = capacity;
}
public int get(int key) {
if(!map.containsKey(key)) {
return -1;
}
int val = map.get(key).value;
put(key, val);
return val;
}
public void put(int key, int value) {
Node node = new Node(key, value);
if (map.containsKey(key)) {
cache.remove(map.get(key));
cache.addFirst(node);
map.put(key, node);
} else {
if (capacity == cache.size()) {
Node last = cache.removeLast();
map.remove(last.key);
}
cache.addFirst(node);
map.put(key, node);
}
}
}
class Node {
public int key, value;
public Node pre, next;
public Node(int key, int value) {
this.key = key;
this.value = value;
}
}
class DoubleList {
private Node head, tail;
private int size;
// 在链表头部添加结点x，时间O(1)
public void addFirst(Node node){
if (head == null) {
head = tail = node;
} else {
Node n = head;
n.pre = node;
node.next = n;
head = node;
}
size ++;
}
// 删除链表中的x结点（x一定存在）
// 由于是双链表且给的是目标Node
public void remove(Node node){
if(head == node && tail == node) {
head = tail = null;
} else if(head == node) {
node.next.pre = null;
head = node.next;
} else if(tail == node) {
tail.pre.next = null;
tail = node.pre;
} else {
node.next.pre = node.pre;
node.pre.next = node.next;
}
size --;
}
// 删除链表中最后一个结点，并返回该结点
public Node removeLast(){
Node node = tail;
remove(tail);
return node;
}
// 返回链表长度
public int size() {
return size;
}
}