LRU management (牛客多校) (map+list)

 

 

 

 思路: 利用map+list暴力模拟就彳于了

unordered_map<string,list<>::iterator > mp

#pragma GCC optimize(2)
#include <bits/stdc++.h>
using namespace std;
#define IOS ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define MAXN 100001
#define INF (0x3f3f3f3f)
#define uint unsigned int
#define ll long long
#define ull unsigned long long
#define lowbit(x) ((x) & -(x))
#define DEBUG(a) cout<<#a<<" = "<<(a)<<endl;
//head
typedef struct Node{
    string id;
    int var;
    Node() {}
    Node(const string &_id, const int &_var): id(_id), var(_var) {}
}Node;
list<Node> link;
unordered_map<string,list<Node>::iterator> mmp;
uint m, M;  //m 当前 cache 大小; M 块大小
void update(string name, int var){
    if(mmp.find(name) == mmp.end()){
        link.push_back(Node(name, var));
        mmp.insert({name, --link.end()});
        if(m == M){
            mmp.erase(link.front().id);
            link.pop_front();
        }else{
            ++m;
        }
        cout << var <<'\n';
    }else{
        auto it = mmp[name];
        cout << it->var <<'\n';
        link.push_back(Node(name, it->var));
        link.erase(it);
        mmp[name] = --link.end();
    }
}
void query(string name, int var){
    if(mmp.find(name) == mmp.end()){
        cout << "Invalid\n";
    }else{
        auto it = mmp[name];
        if(var == 1){
            it = next(it);
            if(it == link.end()){
                cout << "Invalid\n";
            }else{
                cout << it->var << '\n';
            }
        }else if(var == -1){
            if(it == link.begin()){
                cout << "Invalid\n";
            }else{
                it = prev(it);
                cout << it->var << '\n';
            }
        }else{
            cout << it->var << '\n';
        }
    }
}
void solve(){
    link.clear();
    mmp.clear();
    m = 0;
    int Q;
    cin >> Q >> M;
    for(int i = 0;i < Q;++i){
        int op, var;
        string name;
        cin >> op >> name >> var;
        if(op){
            query(name, var);
        }else{
            update(name, var);
        }
    }
}
int main(){
    IOS
    int T;
    cin >> T;
    while(T--){
        solve();
    }
    return 0;
}

list:

• push_back(), pop_front()...
• q.erase(迭代器)
• next(it,val);
• prev(it,val);