objectMainextendsApp{

varreverse_pairs = 0//逆序數

defmsort[T](cmp:(T, T) => Boolean)(l:List[T]):List[T] = {

defmerge(l1:List[T], l2:List[T]):List[T]=(l1, l2)match{

case(Nil, _) => l2

case(_, Nil) => l1

case(x::left1, y::left2) =>

if(cmp(x, y))

x::merge(left1, l2)

else{

reverse_pairs += l1.length

y::merge(l1, left2)

}

}

valn = l.length / 2

if(n == 0)

return l

else{

val(l1, l2) = l.splitAt(n)

merge(msort(cmp)(l1), msort(cmp)(l2))

}

}

println(msort((x:Int, y:Int) => x<y)(List(5, 4, 3, 2, 7,6 )))

println(reverse_pairs)

}