标签：null insert ble pac post integer win you list
Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and put.
get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.put(key, value) - Set or insert the value if the key is not already present. When the cache reached its capacity, it should invalidate the least recently used item before inserting a new item.
Follow up:
Could you do both operations in O(1) time complexity?
Example:
LRUCache cache = new LRUCache( 2 /* capacity */ ); cache.put(1, 1); cache.put(2, 2); cache.get(1); // returns 1 cache.put(3, 3); // evicts key 2 cache.get(2); // returns -1 (not found) cache.put(4, 4); // evicts key 1 cache.get(1); // returns -1 (not found) cache.get(3); // returns 3 cache.get(4); // returns 4
import java.util.HashMap;
public class LRUCache {
private HashMap<Integer, DoubleLinkedListNode> map
= new HashMap<Integer, DoubleLinkedListNode>();
private DoubleLinkedListNode head;
private DoubleLinkedListNode end;
private int capacity;
private int len;
public LRUCache(int capacity) {
this.capacity = capacity;
len = 0;
}
public int get(int key) {
if (map.containsKey(key)) {
DoubleLinkedListNode latest = map.get(key);
removeNode(latest);
setHead(latest);
return latest.val;
} else {
return -1;
}
}
public void removeNode(DoubleLinkedListNode node) {
DoubleLinkedListNode cur = node;
DoubleLinkedListNode pre = cur.pre;
DoubleLinkedListNode post = cur.next;
if (pre != null) {
pre.next = post;
} else {
head = post;
}
if (post != null) {
post.pre = pre;
} else {
end = pre;
}
}
public void setHead(DoubleLinkedListNode node) {
node.next = head;
node.pre = null;
if (head != null) {
head.pre = node;
}
head = node;
if (end == null) {
end = node;
}
}
public void put(int key, int value) {
if (map.containsKey(key)) {
DoubleLinkedListNode oldNode = map.get(key);
oldNode.val = value;
removeNode(oldNode);
setHead(oldNode);
} else {
DoubleLinkedListNode newNode =
new DoubleLinkedListNode(key, value);
if (len < capacity) {
setHead(newNode);
map.put(key, newNode);
len++;
} else {
map.remove(end.key);
end = end.pre;
if (end != null) {
end.next = null;
}
setHead(newNode);
map.put(key, newNode);
}
}
}
}
class DoubleLinkedListNode {
public int val;
public int key;
public DoubleLinkedListNode pre;
public DoubleLinkedListNode next;
public DoubleLinkedListNode(int key, int value) {
val = value;
this.key = key;
}
}
标签：null insert ble pac post integer win you list
原文地址：https://www.cnblogs.com/clarencezzh/p/10919035.html
