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test56.java
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86 lines (77 loc) · 1.92 KB
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package byteDance;
import java.util.HashMap;
import java.util.Map;
/**
* @Author:lizeyang
* @Date:2020/5/23 17:34
* function:LRU实现
*/
public class test56 {
//方法2实现：双链表 + HashMap
class Node {
int key;
int value;
Node pre;
Node next;
Node(int key, int value) {
this.key = key;
this.value = value;
pre = null;
next = null;
}
}
private int capacity;
private Map<Integer, Node> map;
private Node head;
private Node tail;
test56(int capacity) {
this.capacity = capacity;
map = new HashMap<>();
head = new Node(-1, -1);
tail = new Node(-1, -1);
head.next = tail;
tail.pre = head;
}
public int get(int key) {
if (!map.containsKey(key)) {
return -1;
}
Node node = map.get(key);
//先删除节点
node.pre.next = node.next;
node.next.pre = node.pre;
//提高优先级，连接尾部
moveToTail(node);
return node.value;
}
public void put(int key, int value) {
if (get(key) != -1) {
map.get(key).value = value;
return;
}
Node node = new Node(key, value);
map.put(key, node);
moveToTail(node);
if (map.size() > capacity) {
map.remove(head.next.key);
head.next = head.next.next;
head.next.pre = head;
}
}
public void moveToTail(Node node) {
node.pre = tail.pre;
tail.pre = node;
node.pre.next = node;
node.next = tail;
}
public static void main(String[] args) {
test56 test = new test56(3);
test.put(1, 2);
test.put(2, 3);
test.put(3, 4);
test.put(4, 5);
System.out.println(test.get(3));
test.put(2, 3);
System.out.println(test.get(1));
}
}