Group Anagrams
Group a list of words so that anagrams end up together.
Progress cannot be saved in this browser, so completed lessons will reset when you leave.
Lesson notes
Try it before you watch
Restate the problem in your own words, list the edge cases, and sketch a solution with its running time. Then play the video and compare.
Reveal the key idea
Give every word a canonical key, such as its sorted letters or a 26-letter count tuple, and collect words by key in a dictionary.
Pattern: Arrays & hashing. Trade memory for speed: sets and dictionaries answer 'have I seen this?' in O(1).
Complexity
| Measure | Bound |
|---|---|
| Time | O(n · k log k) with sorted keys |
| Extra space | O(n · k) |
Walkthroughs often start from a simpler approach first; aim to reach these bounds. New to Big-O? Read understanding algorithmic complexity.