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The Pattern Playbook: Data Structures and Algorithms: Uncharted

Courses Data Structures and AlgorithmsThe Pattern Playbook

The Pattern PlaybookPro

Recognize pointer, window, prefix, interval, trie, and composite openings quickly.

Data Structures and Algorithms
Unit 15 of 16
20 lessons
136 min
420 XP

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

Lessons

20 total

1Name the MoveRecognize an algorithmic pattern from ordering, contiguity, recency, or state-update constraints rather than story nouns.ProInteractiveConcept6 min20 XPOpen
2Two Pointers, InwardApply inward two-pointer target search to finding a target pair in a sorted array while shrinking both ends.ProCodeConcept6 min20 XPOpen
3The Writer PointerApply read-pointer write-pointer compaction to compacting a sorted array by separating read and write positions.ProCodeConcept6 min20 XPOpen
4The Fixed WindowApply rolling fixed-width sum to finding the best seven-day sales span by rolling one sum.ProCodeConcept6 min20 XPOpen
5The Stretchy WindowApply last-seen variable-width window to expanding a substring and jumping its left edge beyond a repeat.ProCodeConcept6 min20 XPOpen
6Window DrillsApply expand-then-shrink positive-sum window to shrinking a positive-value window to the shortest target-reaching span.ProCodePractice8 min20 XPOpen
7Predict the WindowTrace a sliding window by recording both pointer positions, current contents, and the validity condition.ProInteractiveConcept6 min20 XPOpen
8Prefix SumsApply build-once prefix-sum queries to building an odometer strip so any trip total is one subtraction.ProCodeConcept6 min20 XPOpen
9Prefix DrillsApply prefix-total frequency map to counting target-sum subarrays with prefix frequencies and a hash map.ProCodePractice8 min20 XPOpen
10Monotonic ReturnsApply monotonic decreasing index stack to reusing a decreasing stack to compute each stock span.ProCodeConcept6 min20 XPOpen
11Merge the CalendarApply sorted interval coalescing to flattening overlapping calendar blocks after sorting by start time.ProCodeConcept6 min20 XPOpen
12Interval DrillsApply interval insertion merge and complement scan to inserting a calendar block, merging overlaps, and finding free time.ProCodePractice8 min20 XPOpen
13The Autocomplete TreeApply trie insertion and whole-word lookup to inserting words letter by letter and distinguishing prefixes from whole words.ProCodeConcept6 min20 XPOpen
14Prefix SuggestionsApply prefix descent then trie collection to descending to one search prefix and collecting the words beneath it.ProCodeConcept6 min20 XPOpen
15Trie DrillsApply subtree word-count trie augmentation to augmenting trie nodes with counts for instant prefix totals.ProCodePractice8 min20 XPOpen
16The LRU MachineApply map-backed least-recently-used eviction to keeping recent apps warm with JavaScript Map insertion order and Python OrderedDict recency operations.ProCodeConcept6 min20 XPOpen
17LRU DrillsApply LRU hit-miss and eviction trace to tracing cache hits, misses, recency refreshes, and evictions.ProCodePractice8 min20 XPOpen
18Spot the PatternMatch fresh briefs to two pointers, sliding windows, prefix sums, monotonic stacks, heaps, or hashing from their constraints.ProInteractiveConcept6 min20 XPOpen
19Combine the MovesApply variable window plus frequency map to combining a variable window with a frequency map for at most k distinct characters.ProCodePractice8 min20 XPOpen
20Pattern Playbook Mastery CheckApply two-pointer target plus rolling-window synthesis to combining inward pointers with a rolling fixed-width window.ProCodeMastery check10 min40 XPOpen

Greedy and Backtracking The Gauntlet