1 class LRUCache {
2 public:
3 struct Node
4 {
5 int key;
6 int val;
7 Node( int _k, int _v ) : key( _k ), val( _v )
8 {
9 }
10 };
11 list<Node> l;
12 unordered_map<int, list<Node>::iterator> mp;
13 int size;
14 int capacity;
15 LRUCache( int _capacity ) : capacity( _capacity ), size( 0 )
16 {
17 }
18
19
20 int get( int key )
21 {
22 auto it = mp.find( key );
23 if ( it == mp.end() )
24 return(-1);
25 else{
26 int ans = it->second->val;
27 l.erase( it->second );
28 l.push_front( Node( key, ans ) );
29 it->second = l.begin();
30 return(ans);
31 }
32 }
33
34
35 void put( int key, int value )
36 {
37 auto it = mp.find( key );
38 if ( it != mp.end() )
39 {
40 l.erase( it->second );
41 l.push_front( Node( key, value ) );
42 it->second = l.begin();
43 }else {
44 if ( size < capacity )
45 {
46 l.push_front( Node( key, value ) );
47 mp.insert( { key, l.begin() } );
48 size++;
49 }else {
50 Node node = l.back();
51 l.pop_back();
52 auto rm = mp.find( node.key );
53 mp.erase( rm );
54 l.push_front( Node( key, value ) );
55 mp.insert( { key, l.begin() } );
56 }
57 }
58 }
59 };
