1129 Recommendation System (25 分)

#pragma warning(disable:4996)
#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
#include <map>
#include <set>
using namespace std;
struct node
{
    int ind, num;
    node(int x) :ind(x){}
    node(int x, int y):ind(x), num(y){}
    bool operator < (const node& a)const
    {
        return num != a.num ? num > a.num : ind < a.ind;
    }
};
//int book[50001];
int main()
{
    int n, k;
    cin >> n >> k;
    set<node> s;
    for (int i = 0; i < n; ++i)
    {
        int a;
        scanf("%d", &a);
        if (i != 0)
        {
            printf("%d:", a);
            int cnt = 0;
            for (auto it = s.begin(); it != s.end() && cnt < k; ++cnt, ++it)
            {
                printf(" %d", it->ind);
            }
            cout << endl;
        }
        auto it = s.find({ node(a), });//找到下标为a的元素
        if (it != s.end())
        {
            s.erase(it);
        }
        int t = it->num;
        s.insert({ node(a, t+1)});
    }
    return 0;
}