输入数据:

1 2 3 4 5 6 8 9 11 12 34

输出结果：

6

/**
  * 求中位数
  */

object Median {

  def main (args: Array[String]) {

    val conf = new SparkConf().setAppName("Median").setMaster("local")
    val sc = new SparkContext(conf)

    val data = sc.textFile("E:\\newcode\\MyFirstProject\\data\\Median.txt")

    val words = data.flatMap(_.split(" ")).map(word => word.toInt)
    words.collect().foreach(println)
    val number = words.map(word =>(word/4,word)).sortByKey()
    number.collect().foreach(println)
    val pariCount = words.map(word => (word/4,1)).reduceByKey(_+_).sortByKey()
    pariCount.collect().foreach(println)
    val count = words.count().toInt
    var mid =0
    if(count%2 != 0)
    {
      mid = count/2+1
    }else
    {
      mid = count/2
    }

    var temp =0
    var temp1= 0
    var index = 0
    val tongNumber = pariCount.count().toInt

    var foundIt = false
    for(i <- 0 to tongNumber-1 if !foundIt)
    {
      println(pariCount.collectAsMap()(i).toString);
      temp = temp + pariCount.collectAsMap()(i)
      temp1 = temp - pariCount.collectAsMap()(i)
      if(temp >= mid)
      {
        index = i
        foundIt = true
      }
    }
    val tonginneroffset = mid - temp1

    val median = number.filter(_._1==index).takeOrdered(tonginneroffset)
    sc.setLogLevel("ERROR")
    println(median(tonginneroffset-1)._2)
    sc.stop()

  }
}

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