Status: IN
Frequency-based problems follow a standard two-pass pipeline: Counter construction in O(n) followed by a linear scan over the frequency map, with the scan phase specializing across three modes — uniqueness finding (first/kth element with count==1), extremal extraction (max frequency), and group counting (how many keys match a frequency predicate).
Three unused counter beliefs share the build-then-scan pipeline structure
Depends on (SL): counter-two-pass-uniqueness-pattern, counter-two-pass-max-then-count, counter-then-deduplicate-idiom