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sort-list.py
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sort-list.py
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def sortList(head):
first = head
second = head.next if head else None
while second != None:
if first.val > second.val# merge sort, recursively
def sortList(self, head):
if not head or not head.next:
return head
# divide list into two parts
fast, slow = head.next, head
while fast and fast.next:
fast = fast.next.next
slow = slow.next
second = slow.next
# cut down the first part
slow.next = None
l = self.sortList(head)
r = self.sortList(second)
return self.merge(l, r)
# merge in-place without dummy node
def merge(self, l, r):
if not l or not r:
return l or r
if l.val > r.val:
l, r = r, l
# get the return node "head"
head = pre = l
l = l.next
while l and r:
if l.val < r.val:
l = l.next
else:
nxt = pre.next
pre.next = r
tmp = r.next
r.next = nxt
r = tmp
pre = pre.next
# l and r at least one is None
pre.next = l or r
return head:
first.val, second.val = second.val, first.val
first = first.next
else:
second.val, first.val = first.val, second.val
second = second.next