LRU算法

#include <iostream>
#include <list>
#include <map>
using namespace std;
class LRU {
	struct node {
		int key, val;
		node(int k_ = 0, int v_ = 0) {
			key = k_;
			val = v_;
		}
	};
	public:
		int cap; // 大小
		map<int, list<node>::iterator> mp;
		list<node> lt;
		LRU(int c_ = 0) {
			cap = c_;
		} 
		int getval(int key) {
			if(mp.find(key) == mp.end()) return -1;
			lt.splice(lt.begin(), lt, mp[key]);
			mp[key] = lt.begin();
			return mp[key]->val;
		}
		void setkv(int key, int val) {
			if(mp.find(key) == mp.end()) {
			//	cout << mp.size() << " " << cap << endl;
				if(mp.size() == cap) {
					mp.erase(lt.back().key);
					lt.pop_back();
				}
				lt.push_front(node(key, val));
				mp[key] = lt.begin();
			} else {
				mp[key]->val = val;
				lt.splice(lt.begin(), lt, mp[key]);
				mp[key] = lt.begin();
			}
		}
};
int main() {
	LRU L(3);
	int n;
	cin >> n;
	int op, k, v;
	while(n--) {
		cin >> op;
		if(op) {
			cin >> k;
			cout << L.getval(k) << endl;
		} else {
			cin >> k >> v;
			L.setkv(k, v);
		}
	}
	return 0;
} 
/*
10
0 1 1
0 2 2
0 3 3
0 1 4
0 4 4
1 2


*/