scala 两个Map 集合合并

//参考《快学scala》 集合操作 foldLeft page：180
package alogrithnm

import scala.collection.mutable.Map

object CombineTwoMap {

  def main(args: Array[String]): Unit = {

    val map1 = Map[String, Int]("a" -> 1, "b" -> 1, "c" -> 1)
//val map1 = Map[String, Int]("a" -> 1, "b" -> 1, "c" -> 1,"d"->1,"f"->1,"g"->1)
    val map2 = Map("a" -> 1, "z" -> 1, "c" -> 1, "d" -> 1)

    val result = combinerTwoMap(map1, map2)

    for ((k, v) <- result) {
      println(k + "  " + v)
    }
  }

  def combinerTwoMap(a: Map[String, Int], b: Map[String, Int]): Map[String, Int] = {
      (a /: b) {
        case (map, (k, v)) =>
          println(k + " " + v)
          map + (k -> (v + map.getOrElse(k, 0)))
        case _ =>
          println("not match")
          null
      }
    }
}

时间复杂度O(N）取决于size较小的那个map长度。