没什么问题 一道简单的模拟题

#include <bits/stdc++.h>
using namespace std;
struct node{
    int frequently=0,index=0;
    node(int f,int i):frequently(f),index(i){}
    bool operator <(const node &t)const {
        return this->frequently!=t.frequently?this->frequently>t.frequently:this->index<t.index;
    }
};
set<node>s;
int m[50005];
int main(){
    int N,K,a;
    cin>>N>>K>>a;
    s.insert(node(1,a));
    m[a]++;
    for (int i = 1; i <N ; ++i) {
        cin>>a;
        printf("%d: ",a);
        int k=0;
        for (auto j = s.cbegin(); j !=s.cend() and k<K; ++j) {
            printf("%s%d",j==s.begin()?"":" ",j->index);
            ++k;
        }
        printf("\n");
        auto it=s.find(node(m[a],a));
        if (it!=s.end())
            s.erase(it);
        s.insert(node(++m[a],a));
    }
    return 0;
}