Sorting Algorithms

Learn how different algorithms arrange data into a specific order, a fundamental concept in computer science.

Why is Sorting Important?

Sorting is the process of arranging items in a collection in a specific order (e.g., numerical or alphabetical). It might seem basic, but it's one of the most important concepts in computer science. Many advanced algorithms, like binary search, require a sorted collection to work efficiently. Understanding different sorting algorithms and their trade-offs in terms of time and space complexity is crucial for writing efficient and scalable code.

In this guide, we'll explore some of the most common sorting algorithms. Use the interactive visualizer below to see how each one works step-by-step. Writing merge sort from scratch is intern/new-grad. In later interviews, call the language sort (O(n log n)), know whether it is stable, then apply two pointers or greedy on the sorted result. Do not memorize Java collection class names from old prep books.

Algorithm	Best Time	Average Time	Worst Time	Space
Bubble Sort	O(n)	O(n²)	O(n²)	O(1)
Selection Sort	O(n²)	O(n²)	O(n²)	O(1)
Merge Sort	O(n log n)	O(n log n)	O(n log n)	O(n)

Algorithm

Best Time

Average Time

Worst Time

Space

Bubble Sort

O(n)

O(n²)

O(1)

Selection Sort

O(n²)

O(1)

Merge Sort

O(n log n)

O(n)

function groupAnagrams(strs) { const map = {}; for (let str of strs) { // Create a key by sorting the string's characters const sorted = str.split('').sort().join(''); // If the key doesn't exist, initialize an array if (!map[sorted]) { map[sorted] = []; } // Push the original string to the group map[sorted].push(str); } // Return the values of the map return Object.values(map); };