leetcode-LRU Cache(2014.2.7)
2014-04-15 20:02
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参考的是网上的做法,用的双向链表和哈希,哈希是为了改善链表的查找性能:
struct CacheNode{
int key;int value;
CacheNode(int k,int v):key(k),value(v){}
};
class LRUCache{
public:
LRUCache(int capacity) {
size=capacity;
}
int get(int key) {
if(cacheMap.find(key)==cacheMap.end())
return -1;
else
{
cacheList.splice(cacheList.begin(),cacheList,cacheMap[key]);
cacheMap[key]=cacheList.begin();
return cacheMap[key]->value;
}
}
void set(int key, int value) {
if(cacheMap.find(key)==cacheMap.end())
{
if(cacheList.size()==size){
cacheMap.erase(cacheList.back().key);
cacheList.pop_back();
}
cacheList.push_front(CacheNode(key,value));
cacheMap[key]=cacheList.begin();
}
else{
cacheMap[key]->value=value;
cacheList.splice(cacheList.begin(),cacheList,cacheMap[key]);
cacheMap[key]=cacheList.begin();
}
}
private:
list<CacheNode> cacheList;
unordered_map<int,list<CacheNode>::iterator> cacheMap;
int size;
};