【LeetCode】LRU Cache

设计和实现一个  LRU (最近最少使用) 缓存机制。它应该支持以下操作： 获取数据 

get

put

package letcode;

import java.util.HashMap;
import java.util.Map;

/**
* 双向链表+HashMap
*
* @author zeze
*
*/
public class LRUCache {

public static void main(String[] args) {

/*char key = 0;
int value = 0;
LRUCache obj = new LRUCache(capacity);
int param_1 = obj.get(key);
obj.put(key, value);*/

}

int capacity;
Map<Integer, Node> map = new HashMap<Integer, Node>();
Node head = null;
Node end = null;

public LRUCache(int capacity) {
this.capacity = capacity;
}

public int get(int key) {

if (map.containsKey(key)) {
Node temp = map.get(key);
remove(temp);// 移除节点
setHead(temp);// 将节点设置为头结点
return temp.value;
}
return -1;
}

public void put(int key, int value) {
if (map.containsKey(key)) {// 更新节点
Node old = map.get(key);
old.value = value;
remove(old);
setHead(old);
} else {// 插入节点
Node created = new Node(key, value);
if (map.size() >= capacity) {
map.remove(end.key);// HashMap中移除尾节点
remove(end);// 链表中移除尾节点
setHead(created);
} else {
setHead(created);
}
map.put(key, created);
}
}

private void setHead(Node n) {
n.next = head;
n.pre = null;
if (head != null) {
head.pre = n;
}
head = n;
if (end == null)
end = head;

}

private void remove(Node n) {
if (n.pre != null)
n.pre.next = n.next;
else
head = n.next;
if (n.next != null)
n.next.pre = n.pre;
else
end = n.pre;

}

}

class Node {
int key;
int value;
Node pre;
Node next;

Node(int key, int value) {
this.key = key;
this.value = value;
}
}