Hashmaps & Sets
3 programs — patterns, complexity, and code
| # | Program Name | Pattern | Time | Space | Key Idea | Level |
|---|---|---|---|---|---|---|
| 1 | containsDuplicate | HashSet | O(n) | O(n) | Insert into a set; if the element already exists, a duplicate is found. | Simple |
| 2 | groupAnagrams | HashMap + Sorting | O(n·L·logL) | O(n·L) | Use sorted string as canonical key so all anagrams map to the same bucket. | Middle |
| 3 | longestConsecutive | HashSet | O(n) | O(n) | Only start counting a sequence when num-1 is absent (the sequence head). | Middle |