class Solution:
def __init__(self, head: ListNode):
"""
@param head The linked list's head.
Note that the head is guaranteed to be not null, so it contains at least one node.
"""
self.head = head
self.c = 0
while head:
head = head.next
self.c += 1
def getRandom(self) -> int:
"""
Returns a random node's value.
"""
if self.head:
num = random.randint(0, self.c - 1)
ans = self.head
while num > 0:
ans = ans.next
num -= 1
return ans.val
a = stringToListNode('[1,2,3]')
obj = Solution(a)
obj.getRandom()
def findsize(self, head):
cur = head
size = 0
while cur:
cur = cur.next
size += 1
return size
def sortedListToBST(self, head: ListNode) -> TreeNode:
size = self.findsize(head)
def buildtree(l, r):
nonlocal head
if l > r:
return None
mid = (l + r) // 2
left = buildtree(l, mid - 1)
node = TreeNode(head.val)
head = head.next
node.left = left
node.right = buildtree(mid + 1, r)
return node
if size == 0:
return None
return buildtree(0, size - 1)
a = stringToListNode('[-10,-3,0,5,9]')
Solution().sortedListToBST(a)
class Solution:
def insertionSortList(self, head: ListNode) -> ListNode:
H = head
while head.next:
lastnode = head
head = head.next
p = head.next
h2 = H
if int(head.val) > int(lastnode.val):
lastnode = head
elif int(head.val) <= int(h2.val):
head.next = h2
H = head
else:
while int(head.val) > int(h2.val):
prev = h2
h2 = h2.next
prev.next = head
head.next = h2
lastnode.next = p
head = lastnode
return H
from leetcode.trick.listnode.L import stringToListNode
a = stringToListNode('[4,2,1,3]')
Solution().insertionSortList(a)
self.val = val
self.next = next
class Solution:
def swapNodes(self, head: ListNode, k: int) -> ListNode:
h = head
n = 0
while head:
n += 1
head = head.next
if n < 2:
return h
head = h
nx = 0
while head:
nx += 1
if nx == k:
a = head
if nx == n - k + 1:
b = head
head = head.next
a.val, b.val = b.val, a.val
return h
from leetcode.trick.listnode.L import stringToListNode
a = stringToListNode('[100,90]')
Solution().swapNodes(a, 5)
def reverseList(self, head: ListNode) -> ListNode:
if not head:
return
prev = None
while head:
ne = head.next
head.next = prev
prev = head
head = ne
return prev
from leetcode.trick.listnode.L import stringToListNode
# 递归写法
class Solution:
def reverseList(self, head: ListNode) -> ListNode:
def rec(node1, node2):
if not node2:
return node1
else:
ne = node2.next
node2.next = node1
return rec(node2, ne)
return rec(None, head)
a = stringToListNode('[1,2,3,4,5]')
Solution().reverseList(a)
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。'''
from typing import List
from leetcode.trick.listnode.L import stringToListNode
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class Solution:
def oddEvenList(self, head: ListNode) -> ListNode:
if not head:
return
H = head
l = head
r = head.next
R = r
while r and r.next:
p = r.next
r.next = r.next.next
l.next = p
l, r = l.next, r.next
l.next = R
return H
a = stringToListNode('[2]')
Solution().oddEvenList(a)
return H.next
# 归并+递归 链表递归 特殊递归
class Solution:
def sortList(self, head: ListNode) -> ListNode:
if not head or not head.next: return head # termination.
# cut the LinkedList at the mid index.
slow, fast = head, head.next
while fast and fast.next:
fast, slow = fast.next.next, slow.next
mid, slow.next = slow.next, None # save and cut.
# recursive for cutting.
left, right = self.sortList(head), self.sortList(mid)
# merge `left` and `right` linked list and return it.
h = res = ListNode(0)
while left and right:
if left.val < right.val: h.next, left = left, left.next
else: h.next, right = right, right.next
h = h.next
h.next = left if left else right
return res.next
# 作者：jyd
# 链接：https://leetcode-cn.com/problems/sort-list/solution/sort-list-gui-bing-pai-xu-lian-biao-by-jyd/
# 来源：力扣（LeetCode）
# 著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
b = stringToListNode('[3,4,1,9,18,27,36]')
Solution().sortList(b)