标签：leetcode
https://oj.leetcode.com/problems/lru-cache/
http://blog.csdn.net/linhuanmars/article/details/21310633
public class LRUCache {
public LRUCache(int capacity) {
map = new HashMap<>();
head = null;
tail = null;
this.size = 0;
this.capacity = capacity;
}
public int get(int key) {
Node hit = map.get(key);
if (hit == null)
return -1;
// Remove hit from list.
removeNodeFromList(hit);
// Add hit to the head
addNodeToHead(hit);
return hit.value;
}
// Remove some node from the list
private void removeNodeFromList(Node n)
{
if (n == null)
return;
Node pre = n.pre;
Node next = n.next;
if (pre == null) // node is head
head = next;
else
pre.next = next;
if (next == null) // node is tail
tail = pre;
else
next.pre = pre;
n.pre = null;
n.next = null;
size --;
}
// Add some node to head.
// The node doesn‘t belongs to the list.
private void addNodeToHead(Node n)
{
if (n == null)
return;
if (head == null) // Empty list
{
head = n;
tail = n;
}
else
{
n.next = head;
head.pre = n;
head = n;
}
size ++;
}
public void set(int key, int value) {
Node hit = map.get(key);
if (hit != null)
{
hit.value = value;
map.put(key, hit);
removeNodeFromList(hit);
addNodeToHead(hit);
}
else
{
hit = new Node(key, value);
map.put(key, hit);
if (size == capacity)
{
map.remove(tail.key);
removeNodeFromList(tail);
}
addNodeToHead(hit);
}
}
public void remove(int key)
{
Node hit = map.get(key);
if (hit == null)
return;
// Remove from map
map.remove(hit.key);
// Remove from list
removeNodeFromList(hit);
}
private Node head;
private Node tail;
private Map<Integer, Node> map;
private int size;
private int capacity;
// A doubly linked list node.
private static class Node
{
int key;
int value;
Node next;
Node pre;
public Node(int key, int value)
{
this.key = key;
this.value = value;
this.next = null;
this.pre = null;
}
}
}标签：leetcode
原文地址：http://7371901.blog.51cto.com/7361901/1600813
