Status: IN
The Two Sum family is a canonical instantiation of the hash-then-stream pipeline: the hash map serves as the O(1) preprocessing structure for complement lookup while the single-pass array scan constitutes the streaming phase, with check-before-insert ordering providing construction-based correctness — paralleling palindrome's instantiation through Counter and demonstrating the pipeline's universality across point-lookup and aggregate-frequency query modes.
two-sum exercises hash pipeline with point-lookup semantics complementary to palindrome's frequency semantics
Depends on (SL): two-sum-family-spans-lookup-strategy-space, hash-preprocessing-universal-first-step