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Hashing: Data Structures and Algorithms: Uncharted

Courses Data Structures and AlgorithmsHashing

HashingPro

Turn keys into fast lookups, handle collisions, and reuse map-and-set patterns.

Data Structures and Algorithms
Unit 3 of 16
20 lessons
130 min
420 XP

This unit is part of Pro. Upgrade to open every lesson in it.

Lessons

20 total

1The Coat CheckExplain how hashing routes a key to a bucket and why lookup may still scan a collision chain.ProInteractiveConcept6 min20 XPOpen
2Instant MembershipApply list-scan versus set-membership comparison to comparing a guest-list scan with a set lookup at two sizes.ProCodeConcept6 min20 XPOpen
3Maps and Sets, RefitApply parallel map-and-set indexing to using dict and set beside Map and Set for the same lookup job.ProCodeConcept6 min20 XPOpen
4Build the BucketsApply toy hash-table bucket indexing to placing mail into slots from a tiny hash modulo the bucket count.ProCodeConcept6 min20 XPOpen
5Collisions HappenApply separate-chaining collision handling to keeping two keys that land in one bucket by chaining entries.ProCodeConcept6 min20 XPOpen
6Crowding the SlotsUse load factor to decide when bucket crowding makes a hash table resize.ProInteractiveConcept6 min20 XPOpen
7Tally AnythingApply word-frequency map to finding the group chat’s most-used word with a frequency map.ProCodeConcept6 min20 XPOpen
8First UniqueApply tally-then-order first-unique scan to finding the first non-repeating character after one tally pass.ProCodeConcept6 min20 XPOpen
9Two Sum, at LastApply one-pass complement map to splitting a gift card exactly by replacing nested search with a complement map.ProCodeConcept6 min20 XPOpen
10Predict the MapDetermine the final key-value map after ordered insertions, replacements, and deletions.ProInteractiveConcept6 min20 XPOpen
11Group the AnagramsApply canonical-key anagram grouping to grouping words by a stable character inventory key.ProCodePractice8 min20 XPOpen
12Seen It BeforeApply streaming seen-set detection to detecting duplicate events in a stream.ProCodeConcept6 min20 XPOpen
13Set Algebra at WorkApply union-intersection-difference set algebra to finding who belongs to the union, intersection, and difference of two clubs.ProCodeConcept6 min20 XPOpen
14The Memo PadApply memoized recursive call collapse to memoizing repeated work in a closure until the call counter collapses.ProCodeConcept6 min20 XPOpen
15Keys That LieChoose stable hash keys by contrasting Python hashability with JavaScript object identity.ProInteractiveConcept6 min20 XPOpen
16Dedupe the FeedApply first-occurrence stable deduplication to keeping only the first occurrence while preserving feed order.ProCodePractice8 min20 XPOpen
17Index the InventoryApply build-once id-to-record indexing to building one stockroom index and answering many record queries.ProCodePractice8 min20 XPOpen
18When Order MattersApply map plus sorted-key reporting to combining a map with sorted keys for a deterministic report.ProCodeConcept6 min20 XPOpen
19Hash or Not?Select hashing for direct lookup, membership, grouping, or counting, and reject it when ordered access dominates.ProInteractiveConcept6 min20 XPOpen
20Hashing Mastery CheckApply seen-set and complement-map synthesis to combining membership, frequency, and complement lookup patterns.ProCodeMastery check10 min40 XPOpen

Arrays and Strings Linked Lists