60 lines
2.0 KiB
Markdown
60 lines
2.0 KiB
Markdown
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# Quick Sort
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1. **Time Complexity:** O(n^2) occurs when the picked pivot is always an extreme (smallest or largest) element.
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2. **Space Complexity:** O(n).
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3. **Applications:** Commercial computing, search for information, operations research, event-driven simulation, numerical computations, combinatorial search.
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4. **Founder's Name:** Tony Hoare
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## Steps
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1. Consider the last element of the list as pivot.
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2. Define two variables i and j. Set i and j to first and last elements of the list.
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3. Increment i until list[i] > pivot then stop.
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4. Decrement j until list[j] < pivot then stop.
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5. If i < j then exchange list[i] and list[j].
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6. Repeat steps 3,4 and 5 until i > j.
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7. Exchange the pivot element with list[j] element.
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## Example
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**Given array : [10, 80, 30, 90, 40, 50, 70]**
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**Pivot (last element) : 70**
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**1. 10 < 70 then i++ and swap(list[i],list[j]):** [10, 80, 30, 90, 40, 50, 70]
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**2. 80 < 70, then no actions needed:** [10, 80, 30, 90, 40, 50, 70]
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**3. 30 < 70 then i++ and swap(list[i],list[j]):** [10, 30, 80, 90, 40, 50, 70]
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**4. 90 < 70, then no actions needed:** [10, 30, 80, 90, 40, 50, 70]
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**5. 40 < 70 then i++ and swap(list[i],list[j]):** [10, 30, 40, 90, 80, 50, 70]
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**6. 50 < 70 then i++ and swap(list[i],list[j]):** [10, 30, 40, 50, 80, 90, 70]
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**7. Swap list[i+1] and pivot:** [10, 30, 40, 50, 70, 90, 80]
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**8. Quick sort the left part of the pivot:** [10, 30, 40, 50]
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**9. Quick sort the right part of the pivot:** [70, 80, 90]
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**10. Sorted Array:** [10, 30, 40, 50, 70, 80, 90]
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## Implementation
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- [Java](../../../algorithms/Java/sorting/quick-sort.java)
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- [JavaScript](../../../algorithms/JavaScript/src/sorting/quick-sort.js)
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- [Go](../../../algorithms/Go/sorting/quicksort.go)
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- [C++](../../../algorithms/CPlusPlus/Sorting/quick-sort.cpp)
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- [Python](../../../algorithms/Python/sorting/quicksort.py)
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## Video URL
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[Youtube Video about Quick Sort](https://www.youtube.com/watch?v=PgBzjlCcFvc&ab_channel=GeeksforGeeks)
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## Others
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[Wikipedia](https://en.wikipedia.org/wiki/Quicksort)
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