Question

I’m trying out Scala and I want to see how one would implement insertion sort in scala with the following requirements:

1. Nested for loops
2. Array[Int] for input
3. If possible a way to modify the contents of the function in a call by reference way otherwise return an Array[Int]

If this isn’t the Scala way of implementing insertion sort can you still provide code for the above and explain what is wrong with the approach.
edit:
This is an attempt using a while loop (doest work) and no it isn’t a homework question, why the hostility?

def insert_sort(a:Array[Int]):Array[Int]={
for(i <- 0 until a.length)
{
  var j=i+1

  while(j>1&&a(j)<a(j-1)&&j<a.length)
  {
      var c=a(j)
      a(j)=a(j-1)
      a(j-1)=c
      j-=1
  }
}
return a
}

Answer 1

The implementation given in the wikipedia article fits your bill. Here it is, copied, pasted, and converted to Scala syntax:

def insertionSort(a: Array[Int]): Array[Int] = {
  for (i <- 1 until a.length) {
    // A[ i ] is added in the sorted sequence A[0, .. i-1]
    // save A[i] to make a hole at index iHole
    val item = a(i)
    var iHole = i
    // keep moving the hole to next smaller index until A[iHole - 1] is <= item
    while (iHole > 0 && a(iHole - 1) > item) {
      // move hole to next smaller index
      a(iHole) = a(iHole - 1)
      iHole = iHole - 1
    }
    // put item in the hole
    a(iHole) = item
  }
  a
}