Linked Lists mind map
Rewiring nodes, fast & slow pointers, and list tricks.
Core idea: Node identity matters; save next before changing any arrow.
Mnemonic: Save → rewire → advance · Cost: O(n) time · O(1) pointer space
Guard: Dummy head
Signal: The head might be inserted, removed, or replaced.
Move: Put a stable sentinel before the real list so every mutation has a predecessor.
Examples: Merge Two Lists, Remove Nth Node, Partition List
Flip: Pointer reversal
Signal: Links must reverse wholly, in a range, or in fixed groups.
Move: Carry prev, curr, next; reconnect the reversed region to both untouched boundaries.
Examples: Reverse List, Reverse Between, Reverse K Group
Race: Fast & slow
Signal: You need a midpoint, cycle, or repeated state without extra memory.
Move: Let speed difference reveal the meeting; reset one pointer when locating cycle entry.
Examples: Middle of List, Linked List Cycle II, Find Duplicate
Align: Merge, identity & cloning
Signal: Lists converge, interleave, or carry non-next references.
Move: Equalize remaining distance, merge frontiers, or map originals before wiring copies.
Examples: Intersection of Lists, Merge K Lists, Copy Random List