func doMergeSort(head *list.Node) ( //head != nil
first *list.Node, last *list.Node) {
first, last = head, list.FakeHead(&first)
var size = 0
for ; head != nil; size += 2 {
if head.Next == nil {
last = head
size++
break
}
var node0, node1 = head, head.Next
head = node1.Next
if node0.Val > node1.Val {
last.Next, node1.Next, node0.Next = node1, node0, head
last = node0
} else {
last = node1
}
}
for step := 2; step < size; step *= 2 {
head, last = first, list.FakeHead(&first)
for head != nil {
var left, right, node *list.Node
left, head = head, cutPeice(head, step)
right, head = head, cutPeice(head, step)
last.Next, node = merge(left, right)
last, node.Next = node, head
}
}
return first, last
}
func stupidLinkList(size int) *list.Node {
var head *list.Node
var tail = list.FakeHead(&head)
for i := 0; i < size; i++ {
tail.Next = new(list.Node)
tail = tail.Next
tail.Val = i / 2
}
tail.Next = nil
return head
}
func ramdomLinkList(size int) *list.Node {
rand.Seed(time.Now().Unix())
var head *list.Node
var tail = list.FakeHead(&head)
for i := 0; i < size; i++ {
tail.Next = new(list.Node)
tail = tail.Next
tail.Val = rand.Int()
}
tail.Next = nil
return head
}
func merge(left *list.Node, right *list.Node) (first *list.Node, last *list.Node) {
first, last = nil, list.FakeHead(&first)
for {
last.Next = left
if right == nil {
break
}
for ; left != nil && left.Val <= right.Val; left = left.Next {
last = left
}
last.Next = right
if left == nil {
break
}
for ; right != nil && left.Val > right.Val; right = right.Next {
last = right
}
}
for last.Next != nil {
last = last.Next
}
return first, last
}