The trie seems like a very good idea for your constraints. A “thinking outside the box” alternative: If you can afford some probability of answering “present” for a string that is absent EDIT: if you can afford false positives, use a Bloom filter as suggested by WizardOfOdds in the comments. For k=1, a Bloom filter … Read more
I recently went down this path as well; though it sounds like my application was slightly different. I was interested in approximating set operations on a large number of strings. You do make the key observation that a fast bit vector is required. Depending on what you want to put in your bloom filter, you … Read more
Yes, a lossy hash table or a LRUCache is a data structure with fast O(1) lookup that will only give false negatives — if you ask if “Have I run test X”, it will tell you either “Yes, you definitely have”, or “I can’t remember”. Forgive the extremely crude pseudocode: setup_test_table(): create test_table( some large … Read more
Alex has explained it pretty well. For those who still did not get quite a grasp on it, hopefully this example will help you understand: Lets say I work for Google, in the Chrome team, and I want to add a feature to the browser which notifies the user if the url he has entered … Read more