C++ 代码

#include <iostream>
#include <vector>
#include <unordered_map>
#include <algorithm>
using namespace std;

unordered_map<int, int> freq;

bool cmp(const int& a, const int& b) {
    if (freq[a] != freq[b]) return freq[a] > freq[b];
    else return a < b;
}
int n, k, id;
vector<int> rec;
unordered_map<int, bool> isExist;

int main() {
    scanf("%d%d", &n, &k);
    for (int i = 0; i < n; i++) {
        scanf("%d", &id);
        if (i) {
            printf("%d:", id);
            for (int j = 0; j < rec.size() && j < k; j++) {
                printf(" %d", rec[j]);
            }
            printf("\n");
        }
        //维护 k + 1 大小的数组
        if(isExist[id] == false) {
            isExist[id] = true;
            if (rec.size() > k) {
                isExist[rec[k]] = false;
                rec[k] = id;
            }
            else rec.push_back(id);
        }

        freq[id]++; //更新次数
        sort(rec.begin(), rec.end(), cmp); //按照次数排序
    }
    return 0;
}