游戏中的数学：ELO Rating应用

在之前的博文中简单介绍了ELO Rating系统，依照其思想，博主写了一个对NBA球队的评分系统，代码如下

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;

import javax.sound.sampled.Line;


public class NBAEloRating {
    //根据结果更新A和B的分数
    public static void updateRatingScore(Team teamA, Team teamB, Boolean result){
        final double DEFAULT_ELO_K_FACTOR = 24.0;
        double exceptionA = 1 / (1 + Math.pow(10, (teamB.getRatingScore() - teamA.getRatingScore())/400));
        double exceptionB = 1 - exceptionA;
        double scoreA = -1;
        double scoreB = -1;

        if (result){
            scoreA = 1;
            scoreB = 0;
        }else {
            scoreA = 0;
            scoreB = 1;
        }

        double newArating = teamA.getRatingScore() + DEFAULT_ELO_K_FACTOR * (scoreA - exceptionA);
        double newBrating = teamB.getRatingScore() + DEFAULT_ELO_K_FACTOR * (scoreB - exceptionB);
        teamA.setRatingScore(newArating);
        teamB.setRatingScore(newBrating);
    }

    //输出每个球队的评分
    public static void printRating(ArrayList<Team> teams){
        for (int i = 0; i < teams.size(); i++){
            System.out.print(teams.get(i).getTeamName() + ":");
            System.out.print(teams.get(i).getRatingScore());
            System.out.println();
        }
    }

    public static void main(String[] args) throws IOException{
        ArrayList<Team> teams = computeRatingScore();
        String predictionFilePath = "res\\prediction";
        prediction(teams, predictionFilePath);

    }
    //根据已有的评分，预测比赛结果
    private static void prediction(ArrayList<Team> teams,
            String predictionFilePath) throws IOException {
        String outputPath = "output\\prediction";
        BufferedReader in = new BufferedReader(new FileReader(predictionFilePath));
        String game = in.readLine();
        String output = "";
        while(game != null){
            String temp[] = game.split(" ");
            int teamA = findTeamNo(teams, temp[0]);
            int teamB = findTeamNo(teams, temp[1]);
            double teamAWinPro = computeProbability(teams.get(teamA), teams.get(teamB));
            output += game + " " + teamAWinPro + " " + (1 - teamAWinPro) + "\r\n";
            game = in.readLine();
        }
        File f = new File(outputPath);
        if(!f.exists()){
            f.createNewFile();
        }

        FileWriter fw = new FileWriter(f.getAbsoluteFile());
        BufferedWriter bw = new BufferedWriter(fw);
        bw.write(output);
        bw.close();
    }

    private static double computeProbability(Team teamA, Team teamB) {
        return 1 / (1 + Math.pow(10, (teamB.getRatingScore() - teamA.getRatingScore())/400));
    }

    public static ArrayList<Team> computeRatingScore() throws IOException{
        ArrayList<Team> teams = initailize();
        String dataFilePath = "res\\scoredata";
        BufferedReader in = new BufferedReader(new FileReader(dataFilePath));
        String result = in.readLine();
        while(result != null){
            String temp[] = result.split(" ");
            int teamA = findTeamNo(teams, temp[0]);
            int teamB = findTeamNo(teams, temp[1]);
            boolean rslt = getResult(temp[2]);
            updateRatingScore(teams.get(teamA), teams.get(teamB), rslt);
            result = in.readLine();
        }
        sortByRatingScore(teams);
        printRating(teams);
        return teams;
    }

    private static void sortByRatingScore(ArrayList<Team> teams) {
        Collections.sort(teams, new Comparator<Team>(){

            @Override
            public int compare(Team arg0, Team arg1) {
                double scoreA = arg0.getRatingScore();
                double scoreB = arg1.getRatingScore();
                if (scoreA < scoreB)
                    return 1;
                else {
                    return -1;
                }
            }

        });
    }

    private static boolean getResult(String string) {
        String tmp[] = string.split(":");
        int teamA = Integer.parseInt(tmp[0]);
        int teamB = Integer.parseInt(tmp[1]);
        if (teamA > teamB)
            return true;
        else {
            return false;
        }
    }

    private static int findTeamNo(ArrayList<Team> teams, String teamName) {
        int teamNo = 0;
        while(!teamName.equals(teams.get(teamNo).getTeamName())){
            teamNo++;
        }
        return teamNo;
    }
    //初始化所有球队的评分
    private static ArrayList<Team> initailize() throws IOException {
        ArrayList<Team> teams = new ArrayList<>();
        String teamListFilePath = "res\\teamlist";
        BufferedReader in = new BufferedReader(new FileReader(teamListFilePath));
        String teamName = in.readLine();
        while (teamName != null){
            Team team = new Team(teamName, 1500);
            teams.add(team);
            teamName = in.readLine();
        }
        return teams;
    }
}

public class Team {
    private String teamName;
    private double ratingScore;

    public Team(String teamName, double ratingScore) {
        super();
        this.teamName = teamName;
        this.ratingScore = ratingScore;
    }

    public String getTeamName() {
        return teamName;
    }

    public void setTeamName(String teamName) {
        this.teamName = teamName;
    }

    public double getRatingScore() {
        return ratingScore;
    }

    public void setRatingScore(double ratingScore) {
        this.ratingScore = ratingScore;
    }


}

球队的历史交锋数据保存在scoredata文件中，这个是用爬虫程序抓取出来的，如果想要实现如上的预测系统可以自己写一个爬虫程序，抓取出数据的格式为：

球队A 球队B 比分
譬如：
小牛 马刺 80：99