Linked List

• Cleverly construct a dummy head node. This can make the traversal and processing logic more uniform.
• Use recursion flexibly. By constructing recursive conditions, recursion can be used to solve problems cleverly. However, note that recursion cannot be used for some problems, because excessive recursion depth can cause timeouts and stack overflow.
• Reverse a linked list interval. Problem 92.
• Find the middle node of a linked list. Problem 876. Find the nth node from the end of a linked list. Problem 19. The answer can be obtained with just one traversal.
• Merge K sorted linked lists. Problems 21 and 23.
• Classify linked lists. Problems 86 and 328.
• Sort a linked list, requiring time complexity O(n * log n) and space complexity O(1). There is only one approach: merge sort, top-down merging. Problem 148.
• Determine whether a linked list has a cycle; if it has a cycle, output the index of the intersection point of the cycle; determine whether 2 linked lists have an intersection point; if there is an intersection point, output the intersection point. Problems 141, 142, and 160.

No.	Title	Solution	Difficulty	TimeComplexity	SpaceComplexity	Favorite	Acceptance
0002	Add Two Numbers	[Go]({{< relref "/ChapterFour/0001~0099/0002.Add-Two-Numbers.md" >}})	Medium	O(n)	O(1)		40.4%
0019	Remove Nth Node From End of List	[Go]({{< relref "/ChapterFour/0001~0099/0019.Remove-Nth-Node-From-End-of-List.md" >}})	Medium	O(n)	O(1)		41.1%
0021	Merge Two Sorted Lists	[Go]({{< relref "/ChapterFour/0001~0099/0021.Merge-Two-Sorted-Lists.md" >}})	Easy	O(log n)	O(1)		62.5%
0023	Merge k Sorted Lists	[Go]({{< relref "/ChapterFour/0001~0099/0023.Merge-k-Sorted-Lists.md" >}})	Hard	O(log n)	O(1)	❤️	49.8%
0024	Swap Nodes in Pairs	[Go]({{< relref "/ChapterFour/0001~0099/0024.Swap-Nodes-in-Pairs.md" >}})	Medium	O(n)	O(1)		61.3%
0025	Reverse Nodes in k-Group	[Go]({{< relref "/ChapterFour/0001~0099/0025.Reverse-Nodes-in-k-Group.md" >}})	Hard	O(log n)	O(1)	❤️	54.7%
0061	Rotate List	[Go]({{< relref "/ChapterFour/0001~0099/0061.Rotate-List.md" >}})	Medium	O(n)	O(1)		36.1%
0082	Remove Duplicates from Sorted List II	[Go]({{< relref "/ChapterFour/0001~0099/0082.Remove-Duplicates-from-Sorted-List-II.md" >}})	Medium	O(n)	O(1)		45.9%
0083	Remove Duplicates from Sorted List	[Go]({{< relref "/ChapterFour/0001~0099/0083.Remove-Duplicates-from-Sorted-List.md" >}})	Easy	O(n)	O(1)		50.6%
0086	Partition List	[Go]({{< relref "/ChapterFour/0001~0099/0086.Partition-List.md" >}})	Medium	O(n)	O(1)	❤️	52.0%
0092	Reverse Linked List II	[Go]({{< relref "/ChapterFour/0001~0099/0092.Reverse-Linked-List-II.md" >}})	Medium	O(n)	O(1)	❤️	45.4%
0109	Convert Sorted List to Binary Search Tree	[Go]({{< relref "/ChapterFour/0100~0199/0109.Convert-Sorted-List-to-Binary-Search-Tree.md" >}})	Medium	O(log n)	O(n)		60.2%
0114	Flatten Binary Tree to Linked List	[Go]({{< relref "/ChapterFour/0100~0199/0114.Flatten-Binary-Tree-to-Linked-List.md" >}})	Medium				61.8%
0116	Populating Next Right Pointers in Each Node	[Go]({{< relref "/ChapterFour/0100~0199/0116.Populating-Next-Right-Pointers-in-Each-Node.md" >}})	Medium				60.4%
0138	Copy List with Random Pointer	[Go]({{< relref "/ChapterFour/0100~0199/0138.Copy-List-with-Random-Pointer.md" >}})	Medium				51.4%
0141	Linked List Cycle	[Go]({{< relref "/ChapterFour/0100~0199/0141.Linked-List-Cycle.md" >}})	Easy	O(n)	O(1)	❤️	47.5%
0142	Linked List Cycle II	[Go]({{< relref "/ChapterFour/0100~0199/0142.Linked-List-Cycle-II.md" >}})	Medium	O(n)	O(1)	❤️	48.8%
0143	Reorder List	[Go]({{< relref "/ChapterFour/0100~0199/0143.Reorder-List.md" >}})	Medium	O(n)	O(1)	❤️	52.6%
0146	LRU Cache	[Go]({{< relref "/ChapterFour/0100~0199/0146.LRU-Cache.md" >}})	Medium				40.7%
0147	Insertion Sort List	[Go]({{< relref "/ChapterFour/0100~0199/0147.Insertion-Sort-List.md" >}})	Medium	O(n)	O(1)	❤️	51.1%
0148	Sort List	[Go]({{< relref "/ChapterFour/0100~0199/0148.Sort-List.md" >}})	Medium	O(n log n)	O(n)	❤️	55.1%
0160	Intersection of Two Linked Lists	[Go]({{< relref "/ChapterFour/0100~0199/0160.Intersection-of-Two-Linked-Lists.md" >}})	Easy	O(n)	O(1)	❤️	54.4%
0203	Remove Linked List Elements	[Go]({{< relref "/ChapterFour/0200~0299/0203.Remove-Linked-List-Elements.md" >}})	Easy	O(n)	O(1)		46.0%
0206	Reverse Linked List	[Go]({{< relref "/ChapterFour/0200~0299/0206.Reverse-Linked-List.md" >}})	Easy	O(n)	O(1)		73.6%
0234	Palindrome Linked List	[Go]({{< relref "/ChapterFour/0200~0299/0234.Palindrome-Linked-List.md" >}})	Easy	O(n)	O(1)		50.2%
0237	Delete Node in a Linked List	[Go]({{< relref "/ChapterFour/0200~0299/0237.Delete-Node-in-a-Linked-List.md" >}})	Medium	O(n)	O(1)		76.0%
0328	Odd Even Linked List	[Go]({{< relref "/ChapterFour/0300~0399/0328.Odd-Even-Linked-List.md" >}})	Medium	O(n)	O(1)		61.3%
0382	Linked List Random Node	[Go]({{< relref "/ChapterFour/0300~0399/0382.Linked-List-Random-Node.md" >}})	Medium				62.8%
0445	Add Two Numbers II	[Go]({{< relref "/ChapterFour/0400~0499/0445.Add-Two-Numbers-II.md" >}})	Medium	O(n)	O(n)		59.6%
0460	LFU Cache	[Go]({{< relref "/ChapterFour/0400~0499/0460.LFU-Cache.md" >}})	Hard				43.0%
0622	Design Circular Queue	[Go]({{< relref "/ChapterFour/0600~0699/0622.Design-Circular-Queue.md" >}})	Medium				51.5%
0705	Design HashSet	[Go]({{< relref "/ChapterFour/0700~0799/0705.Design-HashSet.md" >}})	Easy				65.6%
0706	Design HashMap	[Go]({{< relref "/ChapterFour/0700~0799/0706.Design-HashMap.md" >}})	Easy				64.7%
0707	Design Linked List	[Go]({{< relref "/ChapterFour/0700~0799/0707.Design-Linked-List.md" >}})	Medium	O(n)	O(1)		27.7%
0725	Split Linked List in Parts	[Go]({{< relref "/ChapterFour/0700~0799/0725.Split-Linked-List-in-Parts.md" >}})	Medium	O(n)	O(1)		57.2%
0817	Linked List Components	[Go]({{< relref "/ChapterFour/0800~0899/0817.Linked-List-Components.md" >}})	Medium	O(n)	O(1)		57.7%
0876	Middle of the Linked List	[Go]({{< relref "/ChapterFour/0800~0899/0876.Middle-of-the-Linked-List.md" >}})	Easy	O(n)	O(1)	❤️	75.7%
1019	Next Greater Node In Linked List	[Go]({{< relref "/ChapterFour/1000~1099/1019.Next-Greater-Node-In-Linked-List.md" >}})	Medium	O(n)	O(1)		59.9%
1171	Remove Zero Sum Consecutive Nodes from Linked List	[Go]({{< relref "/ChapterFour/1100~1199/1171.Remove-Zero-Sum-Consecutive-Nodes-from-Linked-List.md" >}})	Medium				43.2%
1290	Convert Binary Number in a Linked List to Integer	[Go]({{< relref "/ChapterFour/1200~1299/1290.Convert-Binary-Number-in-a-Linked-List-to-Integer.md" >}})	Easy				82.1%
1669	Merge In Between Linked Lists	[Go]({{< relref "/ChapterFour/1600~1699/1669.Merge-In-Between-Linked-Lists.md" >}})	Medium				73.7%
1670	Design Front Middle Back Queue	[Go]({{< relref "/ChapterFour/1600~1699/1670.Design-Front-Middle-Back-Queue.md" >}})	Medium				57.2%
1721	Swapping Nodes in a Linked List	[Go]({{< relref "/ChapterFour/1700~1799/1721.Swapping-Nodes-in-a-Linked-List.md" >}})	Medium				67.1%
2181	Merge Nodes in Between Zeros	[Go]({{< relref "/ChapterFour/2100~2199/2181.Merge-Nodes-in-Between-Zeros.md" >}})	Medium				86.3%
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