scala之尾递归

object Main extends App {

  def Fibonacci1(n: Int): Int = {
    if (n == 1 || n == 0) 1
    else
      Fibonacci1(n - 1) + Fibonacci1(n - 2)
  }

  def Fibonacci2(n: Int): Int = {
    if (n == 1 || n == 0) 1
    else {
      var lop = 2
      var sum = 0
      while (lop > 0) {
        sum = sum + Fibonacci2(n - lop)
        lop = lop - 1
      }
      sum

    }

  }

  val t1 = System.nanoTime();
  println(Fibonacci1(10))
  val t2 = System.nanoTime();
  println(Fibonacci2(10))
  val t3 = System.nanoTime();
  println(t2 - t1)
  println(t3 - t2)
}

89
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43777662
29317

object Main extends App {

 def sumInts1(a:Int,b:Int,sum:Int):Int={
   if(a>b) sum
   else sumInts1(a+1,b,sum+a)
 }
 def sumInts2(a:Int,b:Int):Int={
   if(a>b) 0
   else
     a+sumInts2(a+1,b)
 }
  val t1 = System.nanoTime();
  println(sumInts1(10,100,0))
  val t2 = System.nanoTime();
  println(sumInts2(10,100))
  val t3 = System.nanoTime();
  println(t2 - t1)
  println(t3 - t2)
}

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