求出 MK 平均值

/*
 * MKAverage class implementation in Java using Java Stream API
 *
 * Thought Process:
 * 1. Initialize the class with m and k values and an empty list to store the stream.
 * 2. For addElement method, add the element to the stream.
 * 3. For calculateMKAverage method, check if the stream has at least m elements.
 *    - If not, return -1.
 *    - Otherwise, get the last m elements, sort them, remove the smallest k and largest k elements, and calculate the average of the remaining elements using streams.
 *    - Return the average after flooring it.
 */
import java.util.*;
import java.util.stream.*;

public class MKAverage {
    private int m, k;
    private List<Integer> stream;

    public MKAverage(int m, int k) {
        this.m = m;
        this.k = k;
        this.stream = new ArrayList<>();
    }

    public void addElement(int num) {
        stream.add(num);
    }

    public int calculateMKAverage() {
        if (stream.size() < m) {
            return -1;
        }
        List<Integer> lastMElements = stream.stream()
                .skip(stream.size() - m)
                .sorted()
                .collect(Collectors.toList());
        for (int i = 0; i < k; i++) {
            lastMElements.remove(0); // Remove smallest k elements
            lastMElements.remove(lastMElements.size() - 1); // Remove largest k elements
        }
        int sum = lastMElements.stream().mapToInt(Integer::intValue).sum();
        return sum / lastMElements.size(); // Floor division
    }
}