Sorted by start time first which is the obvious move, then iterated through comparing end times.
Start by clarifying the problem (e.g., whether intervals are inclusive, if input is sorted, and expected output format). Then propose sorting intervals by start time and merging in a single pass, explaining the O(n log n) time and O(n) space complexity. Walk through an example to demonstrate correctness.
Pro tip: Mention edge cases like empty input, single interval, and intervals that are adjacent but not overlapping (e.g., [1,2] and [2,3]) to show thoroughness. Also, discuss how you would handle large inputs or streaming data if relevant.
Ask about input format, whether intervals are sorted, inclusivity of endpoints, and expected output. Confirm if the result should be sorted.
Propose sorting intervals by start time, then iterating and merging overlapping intervals into a result list. Explain why sorting is necessary.
Describe the merge condition: if the current interval's start <= last merged interval's end, update the end to the max of both ends; otherwise, add the current interval to the result.
State time complexity O(n log n) due to sorting, and space complexity O(n) for the output (or O(1) extra if sorted in-place and output not counted).
Walk through a sample input like [[1,3],[2,6],[8,10],[15,18]] to show the merging process and verify edge cases.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Use DFS/BFS to find each island, then normalize its shape by translating it to a canonical form (e.g., relative coordinates from the top-left cell). Store these normalized shapes in a set to count distinct islands.
Pro tip: Mention that you can optimize by using a hash of the normalized shape (like a string of relative coordinates) to avoid storing large coordinate lists, and discuss trade-offs between different normalization methods.
Iterate through the grid; when you find an unvisited '1', perform DFS/BFS to collect all cells of that island, marking them visited.
Translate the island's coordinates so that the minimum row and column are 0, making the shape invariant to translation.
Convert the normalized coordinates into a canonical representation (e.g., sorted list or string) and insert into a set to track unique shapes.
After processing all islands, the size of the set gives the number of distinct islands.
Discuss time and space complexity: O(R*C) for traversal, and O(R*C) for storing shapes in the worst case.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.