合并scala映射并根据条件更新公共键

debugcn 发表于 Dev

阿拜

我编写了以下代码来合并地图并更新公共键。有没有更好的方法来写这个

  case class Test(index: Int, min: Int, max: Int, aggMin: Int, aggMax: Int)
  def mergeMaps(oldMap: Map[Int, Test], newMap: Map[Int, Test]): Map[Int, Test] = {
    val intersect: Map[Int, Test] = oldMap.keySet.intersect(newMap.keySet)
      .map(indexKey => indexKey -> (Test(newMap(indexKey).index, newMap(indexKey).min, newMap(indexKey).max,
        oldMap(indexKey).aggMin.min(newMap(indexKey).aggMin), oldMap(indexKey).aggMax.max(newMap(indexKey).aggMax)))).toMap
    val merge = (oldMap ++ newMap ++ intersect)
    merge
  }

这是我的测试用例

it("test my case"){
  val oldMap = Map(10 -> Test(10, 1, 2, 1, 2), 25 -> Test(25, 3, 4, 3, 4), 46 -> Test(46, 3, 4, 3, 4), 26 -> Test(26, 1, 2, 1, 2))
  val newMap = Map(32 -> Test(32, 5, 6, 5, 6), 26 -> Test(26, 5, 6, 5, 6))
  val result = mergeMaps(oldMap, newMap)
  //Total elements count should be map 1 elements + map 2 elements
  assert(result.size == 5)
  //Common key element aggMin and aggMax should be updated, keep min aggMin and max aggMax from 2 common key elements and keep min and max of second map key
  assert(result.get(26).get.aggMin == 1)//min aggMin -> min(1,5)
  assert(result.get(26).get.aggMax == 6)//max aggMax -> max(2,6)
  assert(result.get(26).get.min == 5)// 5 from second map
  assert(result.get(26).get.max == 6)//6 from second map
}

jwvh

这是对解决方案的略有不同的看法。

def mergeMaps(oldMap :Map[Int,Test], newMap :Map[Int,Test]) :Map[Int,Test] =
  (oldMap.values ++ newMap.values)
    .groupBy(_.index)
    .map{ case (k,v) =>
      k -> v.reduceLeft((a,b) => 
          Test(k, b.min, b.max, a.aggMin min b.aggMin, a.aggMax max b.aggMax))
    }

我本可以使用groupBy()withmapValues()而不是，map()但这不会导致纯Map.

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