解法一：排序+优先队列

先全部转化为秒来表示，用一个优先队列维护最先可以服务的窗口。

import java.io.*;
import java.util.*;
public class Main {
    private static final int ON = 8 * 3600;
    private static final int OFF = 17 * 3600;
    public static void main(String[] args) throws IOException {
        StreamTokenizer in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        final int N, K;
        in.nextToken();
        N = (int) in.nval;
        in.nextToken();
        K = (int) in.nval;
        ArrayList<Customer> customers = new ArrayList<>(N);
        for (int i = 0, tmp, time; i < N; ++i) {
            in.nextToken();
            tmp = (int) in.nval;
            time = tmp * 3600;
            in.nextToken();
            in.nextToken();
            tmp = (int) in.nval;
            time += tmp * 60;
            in.nextToken();
            in.nextToken();
            tmp = (int) in.nval;
            time += tmp;
            in.nextToken();
            tmp = (int) in.nval;
            if (time <= OFF) {
                customers.add(new Customer(time, tmp * 60));
            }
        }
        Comparator<Customer> customerComparator = new Comparator<Customer>() {
            @Override
            public int compare(Customer o1, Customer o2) {
                return o1.arrive - o2.arrive;
            }
        };
        customers.sort(customerComparator);
        PriorityQueue<Integer> queue = new PriorityQueue<>();
        for (int i = 0; i < K; ++i) {
            queue.offer(ON);
        }
        float wait = 0.0f;
        for (Customer i : customers) {
            int cur = queue.poll();
            if (i.arrive < cur) {
                wait += cur - i.arrive;
                cur += i.process;
            } else {
                cur = i.arrive + i.process;
            }
            queue.offer(cur);
        }
        out.printf("%.1f", wait / customers.size() / 60);
        out.flush();
    }
}
class Customer {
    int arrive;
    int process;
    public Customer(int arrive, int process) {
        this.arrive = arrive;
        this.process = process;
    }
    @Override
    public String toString() {
        return "Customer{" +
                "arrive=" + arrive +
                ", process=" + process +
                '}';
    }
}