//Be careful to use same partioning as in lecture
//and return total number of comparisons
func Quicksort(input sort.IntSlice, ps pivotSelector) int {
if input.Len() < 2 {
return 0
}
input.Swap(0, ps(input))
i := 1
for j := 1; j < input.Len(); j++ {
if input.Less(j, 0) {
input.Swap(i, j)
i++
}
}
input.Swap(0, i-1)
comparisons := input.Len() - 1
comparisons += Quicksort(input[:i-1], ps)
comparisons += Quicksort(input[i:], ps)
return comparisons
}
