core-pattern

In-Place Linked List Manipulation

Reverse, splice, partition, rotate, and delete linked-list nodes safely in place.

Problems

Problems in In-Place Linked List Manipulation

Practice problems that share this primary solution pattern and compare the clues that reveal it.

Group of high school students focused on learning in a computer lab setting.

beginner

10 min read

Merge Two Sorted Lists

The common failure mode here is treating linked lists like arrays: copy the values, sort them, and rebuild. That throws away the structure the problem…

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A serene beach with soft sand, gentle waves, and lush green trees. Perfect for a nature escape.

intermediate

11 min read

Swap Nodes in Pairs

A value swap can produce the right sequence while violating the contract. The real task is to move node identities by changing links—and to do it without…

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Detailed view of ancient stone columns and arches in Athens, showcasing Greek architecture.

advanced

13 min read

Reverse Nodes in k-Group

Reversing a linked-list segment is easy. Preserving everything on both sides of that segment is the real interview problem.

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Close-up of blue ethernet cables hanging in a data center, highlighting technology connections.

intermediate

10 min read

Remove Nth Node From End of List

The target is named from the end, but a singly linked list only lets you move forward. The key move is to convert that backward-looking position into a…

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Close-up of a moss-covered tree trunk in a dark, moody forest setting.

intermediate

10 min read

Partition List

A linked-list partition fails in one of two ways: it loses the unread suffix, or it preserves a stale link and creates the wrong structure. The reliable…

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A sprawling tree with vibrant green leaves creates a serene outdoor scene.

beginner

9 min read

Remove Duplicates from Sorted List

When a problem says “remove duplicates,” the first instinct is often to reach for a set. That works for an unsorted list, but it misses the key clue here:…

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Detailed top view of verdant green leaves showcasing nature's beauty, perfect for botanical themes.

intermediate

11 min read

Remove Duplicates from Sorted List II

The key distinction is easy to miss: this problem removes every node belonging to a repeated value. It does not keep the first occurrence. The solution is…

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Silhouette of a person walking on a vast sand dune in the desert at sunset in Huacachina, Peru.

intermediate

12 min read

Reverse Linked List II

A localized reversal fails at the boundaries: the middle looks correct, but the prefix disappears, the suffix becomes unreachable, or the returned head is…

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Factory chimneys emitting smoke over rooftops on a clear day, illustrating urban pollution.

intermediate

11 min read

Rotate List

A right rotation looks repetitive when described one node at a time. The useful implementation is one split, one reconnection, and one cut.

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