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LRUCache_146.java
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LRUCache_146.java
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import java.util.HashMap;
import java.util.Map;
class LRUCache_146 {
class LinkedNode {
int key;
int value;
public LinkedNode next;
public LinkedNode pre;
LinkedNode(int key, int value) {
this.key = key;
this.value = value;
}
LinkedNode() {
}
}
private Map<Integer, LinkedNode> map;
private int size, capacity;
private LinkedNode head, tail;
private void addNode(LinkedNode node) {
node.next = head.next;
node.pre = head;
head.next.pre = node;
head.next = node;
}
private void removeNode(LinkedNode node) {
LinkedNode pre = node.pre;
LinkedNode next = node.next;
pre.next = next;
next.pre = pre;
}
private void moveToHead(LinkedNode node) {
removeNode(node);
addNode(node);
}
private LinkedNode popTail() {
LinkedNode last = tail.pre;
removeNode(last);
return last;
}
public LRUCache_146(int capacity) {
this.map = new HashMap<>();
this.size = 0;
this.capacity = capacity;
head = new LinkedNode();
tail = new LinkedNode();
head.next = tail;
tail.pre = head;
}
public int get(int key) {
LinkedNode node = map.get(key);
if (node == null) {
return -1;
}
moveToHead(node);
return node.value;
}
public void put(int key, int value) {
LinkedNode node = map.get(key);
if (node == null) {
LinkedNode newNode = new LinkedNode(key, value);
map.put(key, newNode);
addNode(newNode);
if (size == capacity) {
LinkedNode tail = popTail();
map.remove(tail.key);
}
else {
size++;
}
}
else {
node.value = value;
moveToHead(node);
}
}
}
//此题的调库方法,linkedhashmap 一种LRU实现
// class LRUCache EXTENDS LinkedHashMap<Integer, Integer> {
// private int capacity;
// public LRUCache(int capacity) {
// super(capacity, 0.75F, true);
// this.capacity = capacity;
// }
// public int get(int key) {
// return super.getOrDefault(key, -1);
// }
// public void put(int key, int value) {
// super.put(key, value);
// }
// @Override
// protected boolean removeEldestEntry(Map.Entry<Integer, Integer> eldest) {
// return size() > capacity;
// }
// }
/**
* Your LRUCache object will be instantiated and called as such:
* LRUCache obj = new LRUCache(capacity);
* int param_1 = obj.get(key);
* obj.put(key,value);
*/