题解 | #设计LRU缓存结构#利用队列实现，简单
设计LRU缓存结构
http://www.nowcoder.com/practice/e3769a5f49894d49b871c09cadd13a61
import java.util.*;
public class Solution {
/**
* lru design
* @param operators int整型二维数组 the ops
* @param k int整型 the k
* @return int整型一维数组
*/
public int[] LRU (int[][] operators, int k) {
ArrayList<Integer> res = new ArrayList<>();
LinkedList<Integer> stack = new LinkedList<>();
HashMap<Integer,Integer> hm = new HashMap<Integer,Integer>();
for(int i=0;i<operators.length;i++){
int key = operators[i][1];
boolean exist = stack.contains(key);
if(operators[i][0]==1){
hm.put(key, operators[i][2]);
if( exist ){
//若在remove里不强转key对对象类型的话，则将key认为是对应下标的索引，最终会报索引超出异常
stack.remove((Integer)key);
stack.addFirst(key);
}else{
if(stack.size()>=k){
stack.removeLast();
}
stack.addFirst(key);
}
}else if(operators[i][0]==2){
if( exist ){
//若在remove里不强转key对对象类型的话，则将key认为是对应下标的索引，最终会报索引超出异常
stack.remove((Integer)key);
stack.addFirst(key);
res.add(hm.get(key));
}else{
res.add(-1);
}
}
}
int[] r = new int[res.size()];
for(int i=0;i<res.size();i++){
r[i] = res.get(i);
}
return r;
}
} 
