week 6 course

codefabrim · codefabrim · commit 0074d860a0d1 · 2018-11-09T15:35:06.000+01:00
diff --git a/src/main/scala/week6/Maps.sc b/src/main/scala/week6/Maps.sc
@@ -0,0 +1,32 @@
+val capitalOfCountry = Map("US" ->"Washington",
+  "France" -> "Paris",
+  "Germany" -> "Berlin",
+  "Netherland" -> "Den Haag")
+
+capitalOfCountry("US")
+capitalOfCountry("Belgium")
+
+capitalOfCountry get "Belgium"
+capitalOfCountry get "France"
+
+
+
+def showCapital(country: String) : String =
+  capitalOfCountry.get(country) match {
+    case Some(capital) => capital
+    case None => "missing data"
+  }
+
+showCapital("France")
+showCapital("US")
+showCapital("Belgium")
+
+
+
+val fruits = List("apple", "banana","pear", "pineapple", "orange")
+
+fruits.sortWith(_.length < _.length)
+fruits.sorted
+
+
+fruits.groupBy(_.head)
diff --git a/src/main/scala/week6/aroundSet.sc b/src/main/scala/week6/aroundSet.sc
@@ -0,0 +1,60 @@
+val fruits = Set("bananan", "apple", "pear")
+
+val s = (1 to 6).toSet
+val s10 = (1 to 10).toSet
+
+s map (_ +2)
+s.nonEmpty
+
+fruits filter (_ startsWith("app"))
+
+def isSafe(col: Int, queens: List[Int]) : Boolean = {
+  //queens contains col
+  val row = queens.length
+  val queensWithRow = (row -1 to 0  by -1) zip queens
+
+  queensWithRow forall{
+    case (r, c) => col != c  &&  math.abs(col - c)  != row - r
+
+  }
+
+
+}
+
+
+
+def queens(n: Int) : Set[List[Int]] = {
+  def placeQueens(k: Int) : Set[List[Int]] =
+
+    if (k == 0) Set(List())
+    else
+    for {
+      queens <- placeQueens(k -1)
+      col <- 0 until n
+      if isSafe(col, queens)
+
+    } yield col :: queens
+
+
+  placeQueens(n)
+
+
+
+
+}
+
+def show (queens: List[Int]) = {
+
+  val lines =
+    for (col <- queens.reverse)
+      yield Vector.fill(queens.length) ("* ").updated(col, "X ").mkString
+  "\n" + (lines mkString "\n")
+}
+
+
+queens(4)
+queens(4)  map show
+(queens(4)  map show) mkString "\n"
+//(queens(12)  map show) mkString "\n"
+
+
diff --git a/src/main/scala/week6/pairs.sc b/src/main/scala/week6/pairs.sc
@@ -0,0 +1,68 @@
+
+//object pairs {
+  val n = 7
+(1 until n) map (i =>
+    (1 until i) map (j => (i,j)))
+
+// Vector(Vector(),
+// Vector((2,1)),
+// Vector((3,1), (3,2)),
+// Vector((4,1), (4,2), (4,3)),
+// Vector((5,1), (5,2), (5,3), (5,4)),
+// Vector((6,1), (6,2), (6,3), (6,4), (6,5)))
+
+//}
+
+
+
+((1 until n) map (i =>
+  (1 until i) map (j => (i,j)))).flatten
+
+
+//with flatMap  == Map + flatten
+
+(1 until n) flatMap (i =>
+  (1 until i) map (j => (i,j)))
+
+
+
+//now we filter the pair
+def isPrime(n: Int) = (2 until n) forall (n % _ != 0)
+
+(1 until n) flatMap (i =>
+  (1 until i) map (j => (i,j))) filter  (pair =>
+      isPrime(pair._1 + pair._2))
+
+
+
+//for expresseion  in order to make more readable the use
+// of HOF such as map, filter , flatMap
+
+case class Person(name: String, age: Int)
+
+//List[Person]
+val persons = List(Person("tot", 2), Person("papa", 40), Person("mama", 35), Person("child1", 21))
+
+for (p <- persons if p.age > 20) yield p.name
+
+
+
+for {
+  i <- 1 until n   //generator
+  j <- 1 until i
+  if isPrime(i + j)  //filter   here
+} yield (i,j)     // always result as a List
+
+
+
+def scalarProduct(xs: List[Double], ys: List[Double]): Double =
+  (for ((x, y)  <- xs zip ys ) yield  x*y )
+    .sum
+
+val abs = List(1.3,3.2, 45.3)
+val ord = List(76,4, 56.3, 23.1)
+
+scalarProduct(abs,ord)
+
+
+
diff --git a/src/main/scala/week6/polynom.sc b/src/main/scala/week6/polynom.sc
@@ -0,0 +1,14 @@
+
+class Poly(val terms: Map[Int, Double]) {
+  def + (other: Poly) = new Poly(terms ++ other.terms)
+
+  override def toString =
+    (for ((exp, coef) <- terms.toList.sorted.reverse) yield coef + "x^"+ exp) mkString " + "
+
+}
+
+val p1 = new Poly(Map(1->2.0, 3 -> 4.0, 5->6.2))
+val p2 = new Poly(Map(0->3.0,  3->7.0))
+
+p1 + p2
+
