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Solve the Dutch National Flag problem in one pass. How would you handle it?

Python/Codinghard0.5 min readPremium
Frequency
Low
Asked at 1 company
Category
179
questions in Python/Coding
Difficulty Split
127E|24M|28H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Microsoft
Key Concepts Tested
partition
Expert AnswerPremium
103 wordsInterview-ready
**Why Three-Way Partition:** Sort 0s, 1s, 2s in one pass—O(n), O(1). Foundation for 3-way quicksort (Dijkstra's). Used in routing (low/med/high priority), bucketing. **Invariant:** [0..low)=0, [low..mid)=1, [high..n)=2. mid sweeps; swap 0 with low, 2 with high; 1 stays. **Extensions:** K-way partition needs different approach. With duplicates, stability is lost—acceptable for sort....
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