我试图获得一个值，同时使用来自 3 个数组的索引？

Question

name[5] = {Peter, James, Roger, Peter, Josę};

subject[5] = {English, Math, English, Science, Math};

grade[5] = {96, 67, 78, 84, 100};

我在这里想要实现的是获得个人获得最高分的主题。注意名称数组中名称的重复，这是同一个人。我试图做的是使用地图来获得结果，但是对于 3 个数组，对于我目前拥有的 java 级别来说这是相当棘手的。我想获取学生的姓名，将其与他们的成绩相匹配，然后选择成绩最高的学科，所以基本上每个学生姓名的返回值都是一个值。就这样，

英语 数学 英语 数学

Answer 1

我将创建一个名为 getStudentsHighestMark 的方法，该方法获取姓名和成绩数据。该方法将遍历成绩并仅考虑相关学生的成绩。您需要一个 int 来跟踪您看到的该名称的最高成绩，以及该成绩对应的课程的字符串。遍历成绩后，只需返回学生最高分的课程名称。像这样的：

public static void main(String[] args) {
    String[] names = {"Peter", "James", "Roger", "Peter", "Jose"};
    String[] subjects = {"English", "Math", "English", "Science", "Math"};
    int[] grades = {96, 67, 78, 84, 100};

    String petersBest = getStudentsHighestMark("Peter", names, subjects, grades);
    System.out.println("Peter's best is: " + petersBest); //Peter's best is: English
    String jamesBest = getStudentsHighestMark("James", names, subjects, grades);
    System.out.println("James's best is: " + jamesBest);  //James's best is: Math
    String rogersBest = getStudentsHighestMark("Roger", names, subjects, grades);
    System.out.println("Roger's best is: " + rogersBest);  //Roger's best is: English
    String josesBest = getStudentsHighestMark("Jose", names, subjects, grades);
    System.out.println("Jose's best is: " + josesBest);  //Jose's best is: Math
}

private static String getStudentsHighestMark(String name, String[] names, String[] subjects, int[] grades) {
    int highestGrade = 0;
    String bestCourse = "";
    for(int i = 0; i < names.length; i++) {
        if(names[i].equals(name) && grades[i] > highestGrade) {
            highestGrade = grades[i];
            bestCourse = subjects[i];
        }
    }
    return bestCourse;
}

Answer 2

首先我会得到一个与每个名称相关的索引列表：

HashMap<String, List<Integer>> map = new HashMap<String, List<Integer>>();
int index = 0;
for (String n: name) {
    if (!map.containsKey(n)) {
        map.put(n, new ArrayList<Integer>());
    }
    map.get(n).add(index);
    index++;
}

然后我会遍历每个名​​称：

for (String name : map.keySet()) {

获取他们的索引，并找到最高分数的索引：

    List<Integer> indices = map.get(name);
    int maxScore = 0, maxIndex = 0;

    for (int index: indices) {
        if (grades[index] > maxScore) {
            maxIndex = index;
        }
    }

然后我会从主题数组中打印出相同的索引：

    System.out.println(name + " did best in " + subject[index]);
}

Answer 3

Java 8 解决方案：我会编写一个对象并丢弃分数最低的对象。请在下面找到代码 sn-p。

public class Main {

public static void main(String[] args) {
    String[] names = {"Peter", "James", "Roger", "Peter", "Jose"};
    String[] subjects = {"English", "Math", "English", "Science", "Math"};
    int[] grades = {96, 67, 78, 84, 100};
    System.out.println(getStudentWithHighScoredSubjects(names, subjects, grades));
}

public static Map<String, String> getStudentWithHighScoredSubjects(String[] names, String[] subjects, int[] grades) {
    return IntStream.range(0, names.length)
            .mapToObj(i -> new StudentHighestGradeSubject(names[i], subjects[i], grades[i]))
            .collect(Collectors.toMap(StudentHighestGradeSubject::getName, Function.identity(), (s1, s2) -> {
                if (s1.getGrade() > s2.getGrade()) {
                    return s1;
                } else {
                    return s2;
                }
            }, LinkedHashMap::new))
            .entrySet()
            .stream()
            .collect(Collectors.toMap(Map.Entry::getKey, e-> e.getValue().getHighestGradeSubject(), (s1, s2) -> s2, LinkedHashMap::new));
}

private static class StudentHighestGradeSubject {
    private String name;
    private String highestGradeSubject;
    private int grade;

    public StudentHighestGradeSubject(String name, String highestGradeSubject, int grade) {
        this.name = name;
        this.highestGradeSubject = highestGradeSubject;
        this.grade = grade;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getHighestGradeSubject() {
        return highestGradeSubject;
    }

    public void setHighestGradeSubject(String highestGradeSubject) {
        this.highestGradeSubject = highestGradeSubject;
    }

    public int getGrade() {
        return grade;
    }

    public void setGrade(int grade) {
        this.grade = grade;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        StudentHighestGradeSubject that = (StudentHighestGradeSubject) o;
        return Objects.equals(name, that.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name);
    }
}

}

上面给出了执行时的以下输出

{Peter=English, James=Math, Roger=English, Jose=Math}