package com.jackiesteed.leetcode;import java.util.*;/*** Created by jackie on 4/23/15.*/public class LRUCache {private int capacity;private Map<Integer, Ele> map = new HashMap<Integer, Ele>();private Ele head = null;private Ele tail = null;public LRUCache(int capacity) {this.capacity = capacity;}public void set(int key, int value) {if(map.containsKey(key)){Ele e = map.get(key);if(head != e){unlink(e);add2Head(e);}e.value = value;return;}if(map.size() >= capacity){Ele e = tail;map.remove(e.key);e.value = value;e.key = key;map.put(key, e);unlink(e);add2Head(e);return;}Ele e = new Ele();e.key = key;e.value = value;e.pre = null;e.next = null;if(head == null || tail == null){head = e;tail = e;}else{add2Head(e);}map.put(key, e);}private void add2Head(Ele e){e.pre = null;e.next = head;head.pre = e;head = e;}public int get(int key) {if (map.containsKey(key)) {Ele e = map.get(key);if(head != e){unlink(e);add2Head(e);}return map.get(key).value;}return -1;}private void unlink(Ele e){if(e.pre != null)e.pre.next = e.next;if(e.next != null)e.next.pre = e.pre;if(tail == e)tail = e.pre;if(tail == null)tail = head;}static class Ele {private int value;private int key;private Ele next;private Ele pre;}public void print(){Ele e = head;while(true){if(e == null)break;System.out.print("(" + e.key + "," + e.value + "),");e = e.next;}System.out.println("");}public static void main(String[] args) {LRUCache cache = new LRUCache(3);cache.set(1,1);cache.set(2, 2);cache.set(3,3);cache.set(4,4);cache.print();cache.get(4);cache.get(3);cache.get(2);cache.get(1);cache.print();}}