[Java] 期末预测之最佳阈值 202012-2

import java.io.*;
import java.util.*;

class Pair implements Comparable<Pair>
{
    private int y;
    private int result;
    public Pair (int y, int result)
    {
        this.y = y;
        this.result = result;
    }
    public int compareTo (Pair that) {
        return this.y - that.y;
    }
    public String toString() {
        return y   " "   result;
    }
    public int y() {
        return this.y;
    }
    public int result() {
        return this.result;
    }
}

public class Main
{
    public Main() throws IOException
    {
        BufferedReader f = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        StringTokenizer st = null;

        int m = Integer.parseInt(f.readLine());
        Pair[] pairs = new Pair[m];
        for (int i = 0; i < m; i  )
        {
            st = new StringTokenizer(f.readLine());
            int y = Integer.parseInt(st.nextToken());
            int res = Integer.parseInt(st.nextToken());
            pairs[i] = new Pair(y, res);
        }
        Arrays.sort(pairs);

        Map<Integer, Integer> map0 = new HashMap<>();
        for (int i = 0, prev = -1, count = 0; i < m; i  )
        {
            // now the value is bigger than previous one
            if (prev >= 0 && pairs[prev].y() < pairs[i].y()) {
                if (pairs[prev].result() == 0) {
                    map0.put(pairs[i].y(), map0.getOrDefault(pairs[prev].y(), 0)   count);
                }
                else {
                    map0.put(pairs[i].y(), map0.getOrDefault(pairs[prev].y(), 0));
                }
            }
            if (pairs[i].result() == 0) {
                if (prev >= 0 && pairs[prev].y() == pairs[i].y()) {
                    count  ;
                }
                else {
                    count = 1;
                }
                prev = i;
            }
        }

        Map<Integer, Integer> map1 = new HashMap<>();
        for (int i = m - 1, prev = m; i >= 0; i--)
        {
            if (prev < m && pairs[prev].y() > pairs[i].y()) {
                if (pairs[prev].result() == 1) {
                    map1.put(pairs[i].y(), map1.getOrDefault(pairs[prev].y(), 0));
                }
            }
            if (pairs[i].result() == 1) {
                map1.put(pairs[i].y(), map1.getOrDefault(pairs[i].y(), 0)   1);
                prev = i;
            }
        }

        int best_theta = -1, times = 0;
        for (int i = 0; i < m; i  ) {
            int theta = pairs[i].y();
            int temp = map0.getOrDefault(theta, 0)   map1.getOrDefault(theta, 0);
            if (temp >= times) {
                times = temp;
                best_theta = theta;
            }
        }
        out.println(best_theta);

        out.close();
        f.close();
    }

    public static void main(String[] args) throws IOException {
        new Main();
    }

}

来源：https://www.icode9.com/content-1-904401.html