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Thinking on a Number Line
Spot interval problems and learn the master move: sort by start, then sweep once.
Multiple choiceTap - 2
Summary Ranges
Extend a run while numbers stay consecutive — close the range the moment the chain breaks.
Complete codeMultiple choiceTrace - 3
Insert Interval
Three phases, one pass: copy what ends early, absorb every overlap with min/max, copy the rest.
Complete codeCode orderMultiple choiceTrace - 4
Interval List Intersections
Two sorted lists, two pointers: overlap is [max(starts), min(ends)], and only the interval that ends first is finished.
Complete codeDebugMultiple choiceTrace - 5
Non-overlapping Intervals
To remove the fewest intervals, KEEP the most: sort by end and always keep the interval that ends earliest.
Complete codeMultiple choiceTrace - 6
Minimum Arrows to Burst Balloons
The sort-by-end greedy from the other side: shoot at the first end, cover every balloon that starts before it — and here, touching counts.
Complete codeDebugMultiple choiceTrace - 7
Intervals CheckpointCheckpoint
No new concepts — combine the island's interval rules: pick the right sort key, run the overlap test, keep merge bounds honest, and assemble the three-phase insert.
DebugCode orderFill blankMultiple choiceTrace - 8
Intervals ReviewReview
Mixed recap of the island: sort keys, run extension, intersection bounds, the earliest-end greedy, the three-phase insert, and why the sort is the price you pay.
Complete codeDebugCode orderMultiple choiceTapTrace - 9
Boss: Merge IntervalsBoss
The interview classic: sort by start, keep one growing current interval, extend its end with max on every overlap, and emit when the chain breaks.
Complete codeDebugCode orderMultiple choiceTrace
Array Patterns is part of AlgoFox Pro
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