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‎LRUCache.java‎
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‎LRUCache.java‎
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+/*
+ Author:     King, nkuwjg@gmail.com
+ Date:       March 12, 2014
+ Problem:    LRU Cache
+ Difficulty: Hard
+ Source:     http://oj.leetcode.com/problems/lru-cache/
+ Notes:
+ Design and implement a data structure for Least Recently Used (LRU) cache. 
+ It should support the following operations: get and set. 
+ get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.
+ set(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.
+ 
+ Solution: Hash + list.
+*/
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+public class LRUCache {
+    private Map<Integer, Integer> map;
+    private int capacity;
+    public LRUCache(int capacity) {
+        this.capacity = capacity;
+        map = new LinkedHashMap<Integer, Integer>(capacity);
+    }
+    
+    public int get(int key) {
+        Integer val = map.get(key);
+        if (val == null) return -1;
+        map.remove(key);
+        map.put(key, val);
+        return val;
+    }
+    
+    public void set(int key, int value) {
+        map.remove(key);
+        map.put(key, value);
+        if (map.size() > capacity)
+            map.remove(map.entrySet().iterator().next().getKey());
+    }
+}