linked-list-problems.md

Linked List

Basic

Problem	Difficulty
707. Design Linked List	Medium

Traversal

Problem	Difficulty	Notes
2181. Merge Nodes in Between Zeros	Medium (1333)	Sum values until zero, build new node per segment.
817. Linked List Components	Medium (1428)	Check next to see if it's the end.
725. Split Linked List in Parts	Medium	Compute length, distribute remainder one by one.
430. Flatten a Multilevel Doubly Linked List	Medium	Preorder traversal.

• Solved: https://leetcode.com/problems/convert-binary-number-in-a-linked-list-to-integer/description/ 1151
• Solved: https://leetcode.com/problems/find-the-minimum-and-maximum-number-of-nodes-between-critical-points/description/ 1310

Remove

Problem	Difficulty
203. Remove Linked List Elements	Easy
237. Delete Node in a Linked List	Medium
83. Remove Duplicates from Sorted List	Easy
82. Remove Duplicates from Sorted List II	Medium
2487. Remove Nodes From Linked List	Medium (1454)

• Solved: https://leetcode.com/problems/delete-nodes-from-linked-list-present-in-array/description/ 1341

Insert

Problem	Difficulty

• Solved: https://leetcode.com/problems/insert-greatest-common-divisors-in-linked-list/description/ 1279
• https://leetcode.com/problems/insertion-sort-list/description/ m

Reverse

Problem	Difficulty	Notes
206. Reverse Linked List	Easy	Preserve next before reversing.
92. Reverse Linked List II	Medium	Locate beforeLeft and afterRight, then reverse.
24. Swap Nodes in Pairs	Medium
25. Reverse Nodes in k-Group	Hard	Count k nodes, reverse, relink.

• https://leetcode.com/problems/reverse-nodes-in-even-length-groups/description/ 1685

Two Pointers

Problem	Difficulty	Notes
19. Remove Nth Node From End of List	Medium	fast goes n steps, then move together.
61. Rotate List	Medium	fast goes k steps, then move together.
143. Reorder List	Medium	Find middle, reverse second half, merge two halves.
141. Linked List Cycle	Easy	fast and slow move together, if they meet, there is a cycle.
142. Linked List Cycle II	Medium	fast and slow move together, if they meet, there is a cycle.
328. Odd Even Linked List	Medium
86. Partition List	Medium
160. Intersection of Two Linked Lists	Easy	Walk A→B, B→A; meet at intersection.

• https://leetcode.com/problems/swapping-nodes-in-a-linked-list/description/ 1386

Middle

Problem	Difficulty	Notes
876. Middle of the Linked List	Easy	Initialize fast and slow at head, fast goes 2 steps, slow goes 1 step.
2095. Delete the Middle Node of a Linked List	Medium
234. Palindrome Linked List	Easy	Find middle, reverse second half, compare two halves.

• https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/ 1317

Merge

Problem	Difficulty
21. Merge Two Sorted Lists	Easy
2. Add Two Numbers	Medium
23. Merge k Sorted Lists	Hard
1669. Merge In Between Linked Lists	Medium
2181. Merge Nodes in Between Zeros	Medium (1333)

• https://leetcode.com/problems/add-two-numbers-ii/description/ m
• https://leetcode.com/problems/double-a-number-represented-as-a-linked-list/description/ 1393

Other

Problem	Difficulty	Notes
1472. Design Browser History	Medium
138. Copy List with Random Pointer	Medium
146. LRU Cache	Medium
382. Linked List Random Node	Medium
1171. Remove Zero Sum Consecutive Nodes from Linked List	Medium (1782)	Detect repeated prefix sum, cut nodes in between.

---

• https://leetcode.com/problems/lfu-cache/description/ hard
• https://leetcode.com/problems/all-oone-data-structure/description/ hard
• https://leetcode.com/problems/design-skiplist/description/ hard

Explanation

• 725. Split Linked List in Parts
• 206. Reverse Linked List
• 92. Reverse Linked List II
• 143. Reorder List
• 142. Linked List Cycle II
• 146. LRU Cache
• 86. Partition List