EASY NC#35 Blind #40 Linked List

206. Reverse Linked List

📖 Problem

Given the head of a singly linked list, reverse the list, and return the reversed list.

🧠 Visual Learning Aid

1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases

JS/TS Refreshers

  • •Array methods (`push`, `pop`, `shift`, `slice`)
  • •Object/Map/Set usage patterns
  • •Function parameter and return typing

Logical Thinking Concepts

  • •Define invariants before coding
  • •Check edge cases first (`[]`, single element, duplicates)
  • •Estimate time/space before implementation
  • •Apply Recursion reasoning pattern

💡 Approach

  • → Use three pointers: prev, current, next
  • → Save next pointer before changing current.next
  • → Point current.next to prev
  • → Move prev and current forward
  • → Time: O(n), Space: O(1)

🛠️ Hints & Pitfalls

Hints

  • •Use three pointers: prev, current, next
  • •Save next pointer before changing current.next
  • •Point current.next to prev

Common Pitfalls

  • •Move prev and current forward
  • •Time: O(n), Space: O(1)

🧪 Test Cases

Hidden tests on submit: 3

Test Case 1
Not run
Input:
createList([1, 2, 3, 4, 5]);
Expected:
{"val":1,"next":{"val":2,"next":{"val":3,"next":{"val":4,"next":{"val":5,"next":null}}}}}
Test Case 2
Not run
Input:
createList([1]);
Expected:
{"val":1,"next":null}
Test Case 3
Not run
Input:
createList([]);
Expected:
null

📝 Code Editor

📚 Reference Solution

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🔗 Related Problems

#2 Add Two Numbers #19 Remove Nth Node From End of List #21 Merge Two Sorted Lists #23 Merge k Sorted Lists #25 Reverse Nodes in k-Group
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