What is Quick Sort?

Quick Sort is a divide-and-conquer sorting algorithm. It picks a pivot element, partitions the array around it, then recursively sorts the sub-arrays. It’s one of the fastest general-purpose sorting algorithms.

The Basic Idea

Quick sort works by:

Why Quick Sort is Fast

Quick sort is efficient because:

1. Divide-and-conquer: Splits problem into smaller sub-problems
2. In-place: Uses O(log n) extra space (for recursion)
3. Average case: O(n log n) time complexity
4. Cache-friendly: Good locality of reference

Visual Example

Watch quick sort in action:

Click play to see how the algorithm partitions and sorts the array.

Key Characteristics

• Average time: O(n log n) - very fast
• Worst time: O(n²) - rare with good pivot selection
• Space: O(log n) - for recursion stack
• Stable: No - equal elements may change order
• In-place: Yes - sorts the original array

Real-World Use

Quick sort is used in:

• Standard library implementations (C++ std::sort, Java Arrays.sort)
• Database systems
• Operating systems
• Many production applications

What’s Next?

Now that you know what quick sort is, let’s see exactly how it works.