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sorting

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Produce a sorted copy

scala> val a = Array(20, 5, 4)
a: Array[Int] = Array(20, 5, 4)

scala> a.sorted                                                            // gives back a sorted copy
res0: Array[Int] = Array(4, 5, 20)

scala> val b = scala.collection.mutable.ArrayBuffer(20, 5, 4)
b: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(20, 5, 4)

scala> b.sorted                                                            // gives back a sorted copy
res1: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(4, 5, 20)

scala> a
res2: Array[Int] = Array(20, 5, 4)                                         // the original is not changed

scala> b
res3: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(20, 5, 4)    // the original is not changed

Sort an Array in place

scala> a
res4: Array[Int] = Array(20, 5, 4)

scala> scala.util.Sorting.quickSort(a)    // sorts the array in place

scala> a
res6: Array[Int] = Array(4, 5, 20)

Sort an ArrayBuffer

Quicksort doesn't work with array buffers. You can do something like this:

scala> val b = scala.collection.mutable.ArrayBuffer(20, 5, 4)
b: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(20, 5, 4)

scala> scala.util.Sorting.stableSort(b)
res16: Array[Int] = Array(4, 5, 20)        // it gives back a sorted Array

scala> b
res17: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(20, 5, 4)    // but "b" hasn't changed

Or, convert the array buffer to array and use quicksort on this array.