leetcode之LRU Cache

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问题描述如下:

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.

问题链接

考虑使用list(也可以自己实现双向链表)和Map(也可以自己实现hash表)

cpp代码如下:

class LRUCache{private:    typedef struct Node{        int key;        int value;        Node(int k,int v):key(k),value(v){}    }Node;    int cap_;    list<Node> data;    map<int,list<Node>::iterator> quick_find;public:    LRUCache(int capacity) {        cap_=capacity;    }    int get(int key) {        map<int,list<Node>::iterator>::iterator p=quick_find.find(key);        if(p==quick_find.end())return -1;        int value=p->second->value;        data.erase(p->second);        data.push_front(Node(key,value));        quick_find[key]=data.begin();        return value;    }    void set(int key, int value) {        map<int,list<Node>::iterator>::iterator p=quick_find.find(key);        if(p!=quick_find.end()){            data.erase(p->second);            data.push_front(Node(key,value));            quick_find[key]=data.begin();            return;        }        if((int)data.size()<cap_){            data.push_front(Node(key,value));            quick_find[key]=data.begin();        }else{            p=quick_find.find(data.back().key);            quick_find.erase(p);            data.pop_back();            data.push_front(Node(key,value));            quick_find[key]=data.begin();        }    }};


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