Two Pointers Technique

Scenario context

The two pointers technique uses two indices to iterate over a data structure (typically an array or a linked list) to solve problems with optimal time complexity. It is commonly used to find pairs in sorted arrays, reverse structures, or detect cycles.

text Summing elements at pointers: 1 + 10 = 11 (Too small -> Increment left pointer 'i')

┌───┬───┬───┬───┬───┬───┬───┬───┬───┬───┐ │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8…

This walkthrough focuses on Core Mechanism & Implementation.

Before making a design choice, clarify:

• It is commonly used to find pairs in sorted arrays, reverse structures, or detect cycles.
• text Summing elements at pointers: 1 + 10 = 11 (Too small - Increment left pointer 'i') ┌───┬───┬───┬───┬───┬───┬───┬───┬───┬───┐ │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │ 9 │10 │ └───┴───┴───┴───┴───┴───┴───┴───┴───┴───┘ ↑ ↑ i…

Concepts in play: core-algorithm-patterns, caching

Stage 1 — Production Considerations & Trade-offs

• Sum: 2 + 10 = 12 (Too small - Increment left pointer 'i') ┌───┬───┬───┬───┬───┬───┬───┬───┬───┬───┐ │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │ 9 │10 │ └───┴───┴───┴───┴───┴───┴───┴───┴───┴───┘ ↑ ↑ i j Sum: 3 + 10 = 13 (Target Fo…
• Pair is 3 and 10) Observable outcome: Find if a pair exists in a sorted array with a given sum (e.g., Target = 13).
• Initialize : Place two pointers (e.g., i and j ) at desired starting positions (often at the beginning and the end).
• The source focuses on one primary design.

Observable outcome: The source focuses on one primary design.

End-to-end outcome

It is commonly used to find pairs in sorted arrays, reverse structures, or detect cycles.

Alternatives considered

The source focuses on one primary design. A second architecture is not compared, so no alternative is invented here.

Failure and degraded modes

Production Considerations & Trade-offs

• Detection: Sum: 2 + 10 = 12 (Too small - Increment left pointer 'i') ┌───┬───┬───┬───┬───┬───┬───┬───┬───┬───┐ │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │ 9 │10 │ └───┴───┴───┴───┴───┴───┴───┴───┴───┴───┘ ↑ ↑ i j Sum: 3…
• User or operator impact: Sum: 2 + 10 = 12 (Too small - Increment left pointer 'i') ┌───┬───┬───┬───┬───┬───┬───┬───┬───┬───┐ │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │ 9 │10 │ └───┴───┴───┴───┴───┴───┴───┴───┴───┴───┘ ↑ ↑ i j Sum: 3…

• Sum: 2 + 10 = 12 (Too small - Increment left pointer 'i') ┌───┬───┬───┬───┬───┬───┬───┬───┬───┬───┐ │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │ 9 │10 │ └───┴───┴───┴───┴───┴───┴───┴───┴───┴───┘ ↑ ↑ i j Sum: 3 + 10 = 13 (Target Fo…