def generate_test_list2():
n1 = ListNode(1)
n2 = ListNode(2)
n1.next = n2
return n1
def reverseLinkedListII(head, m, n):
if head == None:
return None
dummy = ListNode(0)
dummy.next = head
head = dummy
# find premmNode and mNode
for i in range(1, m):
head = head.next
prevmNode = head
mNode = head.next
# reverse link from m to n
nNode = mNode
nextnNode = nNode.next
for i in range(m, n):
temp = nextnNode.next
nextnNode.next = nNode
nNode = nextnNode
nextnNode = temp
# combine
prevmNode.next = nNode
mNode.next = nextnNode
return dummy.next
def insertAtHead(self, item):
'''
pre: an item to be inserted into list
post: item is inserted into beginning of list
'''
node = ListNode(item)
if not self.length:
# set the cursor to the head because it's the
# first item inserted into the list
self.head = node
elif self.length == 1 and not self.tail:
self.tail = self.head
node.link = self.tail
self.head = node
else:
node.link = self.head
self.head = node
# set the cursor to the head if it's not set yet
if not self.cursor:
self.cursor = self.head
self.length += 1
def oddEvenList(self, head):
"""
:type head: ListNode
:rtype: ListNode
"""
if not head:
return
dummy1, dummy2 = ListNode(0), ListNode(0)
dummy1.next = head
dummy2.next = head.next
dummy3 = head.next
count = 3
while head and dummy3 and dummy3.next and head.next:
if head.next.next and not dummy3.next.next:
head.next = head.next.next
head = head.next
break
elif not head.next.next and dummy3.next.next:
dummy3.next = dummy3.next.next
dummy3 = dummy3.next
break
if count%2:
head.next = head.next.next
head = head.next
else:
dummy3.next = dummy3.next.next
dummy3 = dummy3.next
head.next = dummy2.next
if dummy3:
dummy3.next = None
return dummy1.next
def rotateLSegment(l, m, n):
dummyN = ListNode(0)
dummyN.next = l
l = dummyN
rslt, i = l, 0
while i < m-1:
l = l.next
i += 1
t, i = None, 0
beg, end = l, l.next
l = l.next
while l and i <= n-m:
h = l
l = l.next
h.next = t
t = h
i += 1
beg.next = t
end.next = l
return dummyN.next
def deleteDuplicates(self, head):
"""
:type head: ListNode
:rtype: ListNode
"""
if not head:
return head
# a dummy node is must
dummy = ListNode(0)
dummy.next = head
prev = dummy
current = head
while current:
if current.next and current.val == current.next.val:
# find duplciate, delete all
while current.next and current.val == current.next.val:
current = current.next
# now current pointer is at last node of duplicated
# delete duplicated nodes
prev.next = current.next
current = current.next
# @note: prev stays the same
else:
prev = current
current = current.next
return dummy.next # return could be a empty list, if input list with all duplicates
def revKGroup_r(h, k):
count = 0
dummy = ListNode(-1)
dummy.next = h
n = dummy
head = dummy
while head:
tail = head.next
n = tail
while n and count < k:
n = n.next
count += 1
if count < k and not n:
break
count = 0
stopN = n
head.next = revK_r(tail, stopN)
tail.next = stopN
head = tail
return dummy.next
def test3():
n1 = ListNode(1)
n2 = ListNode(2)
n1.next = n2
ListNode.print_ll(reorderList(n1))
def test3():
n1 = ListNode(1)
n2 = ListNode(2)
n2.next = n1
h = n2
rslt = mergeSort(h)
ListNode.print_ll(rslt)
def generate_test_list3():
n1 = ListNode(1)
n2 = ListNode(2)
n3 = ListNode(3)
n1.next = n2
n2.next = n3
return n1
def addNumbers(h1, h2):
l1, l2 = getLeng(h1), getLeng(h2)
needToAdd1 = addNumRecur(h1, h2, l1 >= l2, abs(l1-l2))
if needToAdd1:
newN = ListNode(1)
newN.next = (h1 if l1>=l2 else h2)
return newN
else:
return (h1 if l1>=l2 else h2)
def test2():
n1a = ListNode(1)
n1b = ListNode(1)
n1c = ListNode(1)
n1a.next = n1b
n1b.next = n1c
rslt = removeElement(n1a, 1)
print(ListNode.print_ll(rslt))
def test_quicksort_list(self):
A = ListNode.makeList([5, 4, 3, 2, 1, 6, 10, 7, 8, 9])
quicksort_list(A, None)
A.show()
A = ListNode.makeList([2, 1, 2, 4, 5, 9, 8])
quicksort_list(A, None)
A.show()
A = ListNode.makeList([10])
quicksort_list(A, None)
A.show()
def removeElement(n, val):
dummyN = ListNode(-1)
dummyN.next = n
h = dummyN
while h:
if h.next and h.next.val == val:
h.next = h.next.next
else:
h = h.next
return dummyN.next
def test004(self):
print "test 004"
n0 = ListNode(0)
n0.next = n0
r = Solution().detectCycle(n0)
print " expect:\t", True
print " output:\t", r
print
def test_hasCycle(self):
s = LeetSolution()
self.assertFalse(s.hasCycle(None))
A = ListNode.makeList([1])
self.assertFalse(s.hasCycle(A))
A.next = A
self.assertTrue(s.hasCycle(A))
A = ListNode.makeList([1, 2, 3, 4, 5])
self.assertFalse(s.hasCycle(A))
A = ListNode.makeList([1, 2, 3, 4, 5])
A.tail.next = A.next.next
self.assertTrue(s.hasCycle(A))
def test_removeNthFromEnd(self):
s = LeetSolution()
head = ListNode.makeList([1, 2, 3, 4, 5])
s.removeNthFromEnd(head, 2).show()
head = ListNode.makeList([1, 2])
s.removeNthFromEnd(head, 1).show()
head = ListNode.makeList([1])
print(s.removeNthFromEnd(head, 1))
head = ListNode.makeList([1, 2])
s.removeNthFromEnd(head, 2).show()
head = ListNode.makeList([1, 2, 3])
s.removeNthFromEnd(head, 3).show()
def removeLinkedListElements(head, val):
if head == None or val == None:
return head
dummy = ListNode(0)
dummy.next = head
head = dummy
while head.next != None:
if head.next.val == val:
head.next = head.next.next
else:
head = head.next
return dummy.next
def test004(self):
print "test 004"
n0 = ListNode(0)
n0.next = n0
hasCycle = Solution().hasCycle(n0)
print " expect:\t", True
print " output:\t", hasCycle
print
def test2():
n1 = ListNode(1)
n1a = ListNode(1)
n1b = ListNode(1)
n2 = ListNode(2)
n3 = ListNode(3)
n1.next = n1a
n1a.next = n1b
n1b.next = n2
n2.next = n3
ListNode.print_ll(removeDupComp(n1))
def test3():
n1 = ListNode(1)
n1a = ListNode(1)
n1b = ListNode(1)
n2a = ListNode(2)
n2b = ListNode(2)
n1.next = n1a
n1a.next = n1b
n1b.next = n2a
n2a.next = n2b
ListNode.print_ll(removeDupComp(n1))
def nthtoLastNodeinList(head, n):
if head is None or n is None:
return None
dummy = ListNode(0)
dummy.next = head
fast = head
slow = head
for i in range(n):
fast = fast.next
while fast is not None:
fast =fast.next
slow = slow.next
return slow
def test_detectCycle(self):
s = LeetSolution()
self.assertEqual(None, s.detectCycle(None))
A = ListNode.makeList([1])
self.assertEqual(None, s.detectCycle(A))
A = ListNode.makeList([1, 2, 3, 4, 5])
self.assertEqual(None, s.detectCycle(A))
A = ListNode.makeList([1])
A.next = A
self.assertEqual(1, s.detectCycle(A).val)
A = ListNode.makeList([1, 2, 3, 4, 5])
A.tail.next = A.next.next
self.assertEqual(3, s.detectCycle(A).val)
def test1():
n0 = ListNode(0)
n1 = ListNode(1)
n2 = ListNode(2)
n3 = ListNode(3)
n4 = ListNode(4)
n0.next = n1
n1.next = n2
n2.next = n3
n3.next = n4
ListNode.print_ll(reorderList(n0))
def removeDuplicatesfromUnsortedList(head):
if head == None:
return None
dummy = ListNode(0)
dummy.next = head
head = dummy
s = set()
while head.next != None:
if head.next.val in s:
head.next = head.next.next
else:
s.add(head.next.val)
head = head.next
return dummy.next
def partition(self, head, x):
"""
:type head: ListNode
:type x: int
:rtype: ListNode
"""
if not head:
return head
# maintain the tail of sub-list with (nodes <= target)
tail = ListNode(0)
tail.next = head
dummy = tail # record it
currentPrev = tail
current = head
# two operation: 1. cut smaller node; 2. insert to sublist
while current:
'''
@note:@memorize:
下面的反人类解法我也给自己跪了，找到比x小的，插入。
一直维护小于x的sublist的tail，被main里的测试fail
其实，维护大于等于x的sublit的head，要更加简单，符合人类思维。。。
'''
if current.val < x: # update tail pointer, but do nothing
# 1. cut
currentPrev.next = current.next
currentForNextLoop = current.next # record it first
# 2. insert
tmp = tail.next
tail.next = current
current.next = tmp
tail = current # update smaller-node-list tail
current = currentForNextLoop # for next loop
# @note: here, no update for currentPrev, still the same one
else:
currentPrev = current
current = current.next
return dummy.next
def removeNthNodefromEndofList(head, n):
if head == None and not n:
return head
dummy = ListNode(0)
dummy.next = head
slow = dummy
fast = dummy
for i in range(n):
fast = fast.next
while fast.next != None:
slow = slow.next
fast = fast.next
slow.next = slow.next.next
return dummy.next
def reverseBetween(self, head, m, n):
"""
:type head: ListNode
:type m: int
:type n: int
:rtype: ListNode
"""
"""
Given: 1->2->3->4->5->NULL, m = 2 and n = 4,
return: 1->4->3->2->5->NULL.
"""
# also need to check list-length >= m,n
if not head or m > n:
return head
dummy = ListNode(0)
dummy.next = head
prev = dummy
current = head
count = 1
while count < m:
prev = current
current = current.next
count += 1
# now current is at m-th node
# @note:@memorize: m-node will always be tail of this local-reversed list
# 1,3,2,4,5 => 1,4,3,2,5
localTail = current
while count < n: # @note:@memorize: note the times of operation, 1-time less
# cache 2 ends, especially current.next, since it will be overwritten
currenthead = prev.next
futureHead = localTail.next
# do the swap
prev.next = futureHead
localTail.next = futureHead.next
futureHead.next = currenthead
count += 1
return dummy.next
def deleteDuplicates(self, head):
if not head:
return head
dummy_head = ListNode(head.val - 1)
dummy_head.next = head
pre = dummy_head
while pre:
cur = pre.next
if cur and cur.next and cur.val == cur.next.val:
while cur and cur.next and cur.val == cur.next.val:
cur = cur.next
pre.next = cur.next
cur = pre.next
else:
pre = cur
return dummy_head.next
def reverseList(self, head):
if not head:
return head
dummy = ListNode(0)
while head:
tmpDummyNext = dummy.next
tmpHeadNext = head.next # @note: should record head.next first: i.e., cut out head node
dummy.next = head
head.next = tmpDummyNext
head = tmpHeadNext # @memorize: stupid, head.next is modified above already!
return dummy.next
def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
x = l1
y = l2
e = 0
root = ListNode(-1)
tail = root
while x != None or y != None:
xv = x.val if x != None else 0
yv = y.val if y != None else 0
res = xv + yv + e
r = res % 10
e = res // 10
rl = ListNode(r)
tail.next = rl
tail = rl
x = x.next if x != None else None
y = y.next if y != None else None
if e != 0:
tail.next = ListNode(1)
return root.next
def deleteDuplicates(self, head):
# write your code here
if head is None:
return head
prehead = ListNode(head.val - 1)
prehead.next = head
node = prehead
while node.next and node.next.next:
if node.next.val == node.next.next.val:
v = node.next.val
tnode = node.next
while tnode:
if tnode.val == v:
tnode = tnode.next
else:
break
node.next = tnode
else:
node = node.next
return prehead.next
def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
add_one = False
sum_node = ListNode(0)
savehead = sum_node
while l1 or l2 or add_one:
sum_node.next = ListNode(0)
sum_node = sum_node.next
if l1:
sum_node.val += l1.val
l1 = l1.next
if l2:
sum_node.val += l2.val
l2 = l2.next
if add_one:
sum_node.val += 1
add_one = False
if sum_node.val >= 10:
sum_node.val -= 10
add_one = True
return savehead.next
def addTwoNumbersHelper(l1, l2):
l1_p, l2_p = l1, l2
carry, dummy_result = 0, ListNode(-1)
tail = dummy_result
while l1_p or l2_p or carry:
l1_val = 0 if not l1_p else l1_p.val
l2_val = 0 if not l2_p else l2_p.val
cur_sum = l1_val + l2_val + carry
tail.next = ListNode(cur_sum % 10)
tail = tail.next
carry = cur_sum / 10
if l1_p: l1_p = l1_p.next
if l2_p: l2_p = l2_p.next
return dummy_result.next
def merge_two_sorted_lists(l1, l2):
dummy_head = tail = ListNode()
while l1 and l2:
if l1.data > l2.data:
tail.next, l2 = l2, l2.next
else:
tail.next, l1 = l1, l1.next
tail = tail.next
tail.next = l1 or l2
return dummy_head.next
def partition(self, head: ListNode, x: int) -> ListNode:
if not head:
return None
list_left = ListNode(201)
list_right = ListNode(201)
sentinel_left = list_left
sentinel_right = list_right
while head:
if head.val < x:
list_left.next = ListNode(head.val)
list_left = list_left.next
else:
list_right.next = ListNode(head.val)
list_right = list_right.next
head = head.next
list_left.next = sentinel_right.next
return sentinel_left.next
def remove_kth_last(L, k):
dummy_head = ListNode(0, L)
first = dummy_head.next
for _ in range(k):
first = first.next
second = dummy_head
while first:
first, second = first.next, second.next
second.next = second.next.next
return dummy_head.next
def removeElements(self, head, val):
"""
算法：dummy节点
思路：
设置dummy节点，head节点向后遍历，如果找到==val的head就删除，否则的话指针向后挪
复杂度分析：
时间：ON
空间：O1
"""
dummy = ListNode(0)
dummy.next = head
pre = dummy
while head:
if head.val == val:
pre.next = head.next
head = pre.next
else:
head = head.next
pre = pre.next
return dummy.next
def swapPairs0(self, head):
"""
do as they say
按照人家的要求来
"""
if head == None or head.next == None:
return head
dummy = ListNode(0)
p = dummy
dummy.next = head
while p and p.next and p.next.next:
first = p.next
second = p.next.next
third = p.next.next.next
p.next = second
second.next = first
first.next = third
p = first
return dummy.next
def mergeKLists_bruteforce(self, lists):
"""
算法："暴力"求解
遍历链表，将所有元素添加进一个list，对list排序后构建成链表的形式
复杂度分析：
时间：Onlogn，转为list要On，排序Onlogn，转成链表On，共Onlogn
空间：On，sort的空间+最后新建后返回的On长度的链表
"""
nodes = []
for i in range(len(lists)):
head = lists[i]
while head != None:
nodes.append(head.val)
head = head.next
nodes.sort()
dummy = ListNode(0)
p = dummy
for x in nodes:
p.next = ListNode(x)
p = p.next
return dummy.next
def even_odd_merge_original(L):
if not L: return L
even_head = even_tail = ListNode(0, None)
odd_head = odd_tail = ListNode(0, None)
curr = L
while curr:
if curr.data % 2 == 0:
even_tail.next = curr
even_tail = curr
else:
odd_tail.next = curr
odd_tail = curr
curr = curr.next
even_tail.next = odd_head
odd_tail.next = None
return even_head.next
def addTwoNumbers(n1, n2, co):
if n1 is None and n2 is None:
if co == 0:
return None
return ListNode(co)
n1_val = 0
n2_val = 0
if n1 is not None:
n1_val = n1.val
if n2 is not None:
n2_val = n2.val
s = n1_val + n2_val + co
new_n = ListNode(s % 10)
n1_next = None if n1 is None else n1.next
n2_next = None if n2 is None else n2.next
new_n.next = addTwoNumbers(n1_next, n2_next, s / 10)
return new_n
def reverseBetween(self, head: ListNode, m: int, n: int) -> ListNode:
if m == n:
return head
dummy = ListNode(-1)
dummy.next = head
pre, cur = None, dummy
for _ in range(m):
pre, cur = cur, cur.next
pos = pre
pre, cur = cur, cur.next
for _ in range(m, n):
cur.next, pre, cur = pre, cur, cur.next
pos.next.next = cur
pos.next = pre
return dummy.next
def removeDupComp(head):
"""
Got this first try. 96.2% - 39.0% performance
"""
if not head: return None
dummy = ListNode(head.val - 1)
dummy.next = head
i, j = dummy, dummy.next
while j:
if i.next == j:
j = j.next
elif i.next.val == j.val:
while j and i.next.val == j.val:
j = j.next
i.next = j
else:
i = i.next
j = j.next
return dummy.next
def mergeTwoLists(self, l1, l2):
cur = dummy = ListNode(0)
while l1 and l2:
if l1.val <= l2.val:
cur.next = l1
l1 = l1.next
else:
cur.next = l2
l2 = l2.next
cur = cur.next
cur.next = l1 or l2
return dummy.next
def deleteDuplicates(self, head: ListNode) -> ListNode:
sentinel = ListNode(101, head)
pred = sentinel
while head:
if head.next and head.val == head.next.val:
while head.next and head.val == head.next.val:
head = head.next
pred.next = head.next
else:
pred = head
head = head.next
return sentinel.next
def partition_(self, head, x):
"""
算法：与上述方法相似，不同的是这里每次创建新的节点，这样最后就不用q.next = None了，但是这样会增大空间复杂度
时间：ON，遍历原链表需要On
空间：ON，两个辅助链表需要ON+ON，故总ON
"""
left = ListNode(0)
p = left
right = ListNode(0)
q = right
while head != None:
if head.val < x:
p.next = ListNode(head.val)
p = p.next
else:
q.next = ListNode(head.val)
q = q.next
head = head.next
p.next = right.next
return left.next
def reorderList(self, head: ListNode) -> None:
"""
Do not return anything, modify head in-place instead.
"""
dummy = ListNode(0)
dummy.next = head
fast = slow = dummy
while fast and fast.next:
slow = slow.next
fast = fast.next.next
ReverseHead = self.__reverse(slow.next)
slow.next = None
ptr1 = head
ptr2 = ReverseHead
while ptr1 and ptr2:
tmp1 = ptr1.next
tmp2 = ptr2.next
ptr1.next = ptr2
ptr2.next = tmp1
ptr1 = tmp1
ptr2 = tmp2
def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
if head is None or n < 0:
return None
dummy_head = ListNode(-1)
dummy_head.next = head
node1 = dummy_head
node2 = dummy_head
for i in range(n):
node1 = node1.next
if node1 is None:
return None
while node1.next is not None:
node1 = node1.next
node2 = node2.next
node2.next = node2.next.next
return dummy_head.next
def main():
node7 = ListNode('7', None)
node6 = ListNode('6', node7)
node5 = ListNode('5', node6)
node4 = ListNode('4', node5)
node3 = ListNode('3', node4)
node2 = ListNode('2', node3)
node1 = ListNode('1', node2)
node0 = ListNode('0', node1)
newhead = reverse_single_linked_list(node0)
while newhead:
print(newhead.val)
newhead = newhead.next
def insert(
self, index, data
): #runs in O(n) time. #we are inserting the data at the index you assign to.
newNode = ListNode(data, None, None)
itrNode = self.__start
counter = 1
while (
counter < index
): # we are going to loop based on where we want to insert the new node
itrNode = self.__start.getNext()
# this iteraters through each node
counter = counter + 1 # we are keeping track of whwere the index is in the linked list.
if (index == 0):
self.push_front(data)
elif (index > self.__length):
self.push_back(data)
else:
#A in the code will be itrNode
#B in the code will be itrNode.getPrevious();
A = itrNode
B = itrNode.getPrevious()
newNode.setPrevious(B)
newNode.setNext(A)
B.setNext(newNode)
A.setPrevious(newNode)
def sortList2(self, head):
"""
Disscussion QuickSort
算法：快排
思路：
快排的链表写法，要注意一些dummy节点的运用，以及记录pre和post等
复杂度分析：
时间：NLOGN
空间：01，不考虑递归栈的话
"""
def partition(start, end):
node = start.next.next
pivotPrev = start.next
pivotPrev.next = end
pivotPost = pivotPrev
while node != end:
temp = node.next
if node.val > pivotPrev.val:
node.next = pivotPost.next
pivotPost.next = node
elif node.val < pivotPrev.val:
node.next = start.next
start.next = node
else:
node.next = pivotPost.next
pivotPost.next = node
pivotPost = pivotPost.next
node = temp
return [pivotPrev, pivotPost]
def quicksort(start, end):
if start.next != end:
prev, post = partition(start, end)
quicksort(start, prev)
quicksort(post, end)
newHead = ListNode(0)
newHead.next = head
quicksort(newHead, None)
return newHead.next
def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
if l1 is None:
return l2
if l2 is None:
return l1
newhead = ListNode(-1, None)
returnhead = newhead
while l1 and l2:
if l1.val < l2.val:
newhead.next = l1
l1 = l1.next
else:
newhead.next = l2
l2 = l2.next
newhead = newhead.next
if l1:
newhead.next = l1
if l2:
newhead.next = l2
return returnhead.next
def test3():
n1 = ListNode(1)
n2 = ListNode(2)
n1.next = n2
ListNode.print_ll(reorderList(n1))
def swapPairs(self, head):
"""
My Method
算法：倒插
思路：
本题思路比较直观，就是新建一个dummy，然后给原链表也建一个头节点，每两个结点倒插
到新的dummy后，如果出现落单的那直接在尾部插入其即可，说明一定是最后一个结点了，
9=2*4+1，8=2*4
要注意的是每次倒插完之后要将p.next 置None，断掉尾部节点与原链表之间的关系
复杂度分析：
时间：ON，遍历一遍链表
空间：O1，常数级
"""
if head == None or head.next == None:
return head
dummy = ListNode(0)
p = dummy
dummy_head = ListNode(0)
dummy_head.next = head
while dummy_head.next != None:
if dummy_head.next.next != None:
p.next = dummy_head.next.next
tmp = dummy_head.next
dummy_head.next = dummy_head.next.next.next
p = p.next
p.next = tmp
else:
p.next = dummy_head.next
dummy_head.next = None
p = p.next
p.next = None
return dummy.next
def deleteDuplicates3(self, head: ListNode) -> ListNode:
dummy = ListNode(-1)
pre, cur = dummy, head
while cur:
if cur.next and cur.next.val == cur.val:
while cur.next and cur.val == cur.next.val:
cur = cur.next
else:
pre.next = cur
pre = pre.next
cur = cur.next
pre.next = None
return dummy.next
def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
sentinel = ListNode()
head = sentinel
while l1 and l2:
if l1.val > l2.val:
head.next = l2
l2 = l2.next
else:
head.next = l1
l1 = l1.next
head = head.next
head.next = l1 or l2
return sentinel.next
def removeNthFromEnd(head: ListNode, n: int) -> ListNode:
first = head
while n:
n -= 1
first = first.next
result = ListNode(0, head)
second = result
while first:
first = first.next
second = second.next
second.next = second.next.next
return result.next
def merge(self, l1, l2):
dummy = ListNode(-1)
curr = dummy
while l1 and l2:
if l1.val < l2.val:
curr.next = l1
l1 = l1.next
else:
curr.next = l2
l2 = l2.next
curr = curr.next
curr.next = l1 if l1 else l2
return dummy.next
def reverse_between(self, head, m, n):
dummy = ListNode(-1, head)
pre_m = self.find_k_th(dummy, m - 1)
m_th = pre_m.next
n_th = self.find_k_th(dummy, n)
post_n = n_th.next
n_th.next = None
self.reverse(m_th)
pre_m.next = n_th
m_th.next = post_n
return dummy.next