Scala应用实例之统计学生成绩

学生的成绩清单格式如下所示，第一行为表头，各字段意思分别为学号、性别、课程名1、课程名 2 等，后面每一行代表一个学生的信息，各字段之间用空白符隔开

Id gender Math English Physics
301610 male 80 64 78
301611 female 65 87 58
...

给定任何一个如上格式的清单（不同清单里课程数量可能不一样），要求尽可能采用函数式编程，统计出各门课程的平均成绩，最低成绩，和最高成绩；另外还需按男女同学分开，分别统计各门课程的平均成绩，最低成绩，和最高成绩。

测试样例 1 如下：

Id gender Math English Physics
301610 male 80 64 78
301611 female 65 87 58
301612 female 44 71 77
301613 female 66 71 91
301614 female 70 71 100
301615 male 72 77 72
301616 female 73 81 75
301617 female 69 77 75
301618 male 73 61 65
301619 male 74 69 68
301620 male 76 62 76
301621 male 73 69 91
301622 male 55 69 61
301623 male 50 58 75
301624 female 63 83 93
301625 male 72 54 100
301626 male 76 66 73
301627 male 82 87 79
301628 female 62 80 54
301629 male 89 77 72，

样例 1 的统计结果输出为：

course average min max
Math: 69.20 44.00 89.00
English: 71.70 54.00 87.00
Physics: 76.65 54.00 100.00
course average min max (males)
Math: 72.67 50.00 89.00
English: 67.75 54.00 87.00
Physics: 75.83 61.00 100.00
course average min max (females)
Math: 64.00 44.00 73.00
English: 77.63 71.00 87.00
Physics: 77.88 54.00 100.00

测试样例 2

Id gender Math English Physics Science
301610 male 72 39 74 93
301611 male 75 85 93 26
301612 female 85 79 91 57
301613 female 63 89 61 62
301614 male 72 63 58 64
301615 male 99 82 70 31
301616 female 100 81 63 72
301617 male 74 100 81 59
301618 female 68 72 63 100
301619 male 63 39 59 87
301620 female 84 88 48 48
301621 male 71 88 92 46
301622 male 82 49 66 78
301623 male 63 80 83 88
301624 female 86 80 56 69
301625 male 76 69 86 49
301626 male 91 59 93 51
301627 female 92 76 79 100
301628 male 79 89 78 57
301629 male 85 74 78 80

样例 2 的统计结果为：

course average min max
Math: 79.00 63.00 100.00
English: 74.05 39.00 100.00
Physics: 73.60 48.00 93.00
Science: 65.85 26.00 100.00
course average min max
Math: 77.08 63.00 99.00
English: 70.46 39.00 100.00
Physics: 77.77 58.00 93.00
Science: 62.23 26.00 93.00
course average min max
Math: 82.57 63.00 100.00
English: 80.71 72.00 89.00
Physics: 65.86 48.00 91.00
Science: 72.57 48.00 100.00

import scala.io.Source

object Main {
  def main(args: Array[String]): Unit = {
    val stuScore=Source.fromFile("ScalaProject/data/StuScore.txt").getLines().toList //读取每行的数据生成一个字符串列表
    val all_score=stuScore
      .map(_.split("\\s+").toList).toList //将每一行转换为一个字符串列表
      .transpose //取出每一列的元素形成新的二维列表
      .drop(2) //去除开头两行
      .groupBy(_(0)) //通过科目分组
      .mapValues(_.flatten.tail.map(_.toDouble)) //对于每一个科目的各个学员的分数列表扁平化转换为Double类型
      .mapValues(x=>{(x.sum/x.size,x.min,x.max)}) //得到每一科的平均值，最小值，最大值
    //相比于上面的，下面多了一个性别分组的操作
    val male_score=stuScore.map(_.split("\\s+").toList).toList.filter(row=> row(1)=="male"||row(1)=="gender").transpose.drop(2).groupBy(_(0)).mapValues(_.flatten.tail.map(_.toDouble)).mapValues(x=>{(x.sum/x.size,x.min,x.max)})
    val female_score=stuScore.map(_.split("\\s+").toList).toList.filter(row=> row(1)=="female"||row(1)=="gender").transpose.drop(2).groupBy(_(0)).mapValues(_.flatten.tail.map(_.toDouble)).mapValues(x=>{(x.sum/x.size,x.min,x.max)})
    println("course\taverage\tmin\tmax")
    all_score.foreach(x=>{print(s"${x._1}\t${x._2._1}\t${x._2._2}\t${x._2._3}\n")})
    println("course\taverage\tmin\tmax")
    male_score.foreach(x=>{print(s"${x._1}\t${x._2._1}\t${x._2._2}\t${x._2._3}\n")})
    println("course\taverage\tmin\tmax")
    female_score.foreach(x=>{print(s"${x._1}\t${x._2._1}\t${x._2._2}\t${x._2._3}\n")})
  }
}