A collection of LeetCode novel solutions that is implemented in Java. It would support you to solve the problems from easy to hard by the simplest ways.
| # | Problem | Difficulty | Source code | Solution |
|---|---|---|---|---|
| 1 | Two Sum | Medium | Java | 1. Hash O(n) and O(n) space. 2. Sort and search with two points O(n) and O(1) space. |
| 2 | Add Two Numbers | Medium | Java | Take care of the carry from lower digit. |
| --- | To-be-updated soon | ---------- | ----------- | -------- |
Below are the Big O performance of common functions of different Java Collections.
| List | Add | Remove | Get | Contains | Next | Data Structure |
|---|---|---|---|---|---|---|
| ArrayList | O(1) | O(n) | O(1) | O(n) | O(1) | Array |
| LinkedList | O(1) | O(1) | O(n) | O(n) | O(1) | Linked List |
| Set | Add | Remove | Contains | Next | Size | Data Structure |
|---|---|---|---|---|---|---|
| HashSet | O(1) | O(1) | O(1) | O(h/n) | O(1) | Hash Table |
| LinkedHashSet | O(1) | O(1) | O(1) | O(1) | O(1) | Hash Table + Linked List |
| EnumSet | O(1) | O(1) | O(1) | O(1) | O(1) | Bit Vector |
| TreeSet | O(log n) | O(log n) | O(log n) | O(log n) | O(1) | Red-black tree |
| ConcurrentSkipListSet | O(log n) | O(log n) | O(log n) | O(1) | O(n) | Skip List |
- Note: h is the table capacity
| Queue | Offer | Peak | Poll | Remove | Size | Data Structure |
|---|---|---|---|---|---|---|
| PriorityQueue | O(log n) | O(1) | O(log n) | O(n) | O(1) | Priority Heap |
| LinkedList | O(1) | O(1) | O(1) | O(1) | O(1) | Array |
| ArrayDequeue | O(1) | O(1) | O(1) | O(n) | O(1) | Linked List |
| ConcurrentLinkedQueue | O(1) | O(1) | O(1) | O(n) | O(n) | Linked List |
| ArrayBlockingQueue | O(1) | O(1) | O(1) | O(n) | O(1) | Array |
| PriorirityBlockingQueue | O(log n) | O(1) | O(log n) | O(n) | O(1) | Priority Heap |
| SynchronousQueue | O(1) | O(1) | O(1) | O(n) | O(1) | None! |
| DelayQueue | O(log n) | O(1) | O(log n) | O(n) | O(1) | Priority Heap |
| LinkedBlockingQueue | O(1) | O(1) | O(1) | O(n) | O(1) | Linked List |
| Map | Get | ContainsKey | Next | Data Structure |
|---|---|---|---|---|
| HashMap | O(1) | O(1) | O(h / n) | Hash Table |
| LinkedHashMap | O(1) | O(1) | O(1) | Hash Table + Linked List |
| IdentityHashMap | O(1) | O(1) | O(h / n) | Array |
| WeakHashMap | O(1) | O(1) | O(h / n) | Hash Table |
| EnumMap | O(1) | O(1) | O(1) | Array |
| TreeMap | O(log n) | O(log n) | O(log n) | Red-black tree |
| ConcurrentHashMap | O(1) | O(1) | O(h / n) | Hash Tables |
| ConcurrentSkipListMap | O(log n) | O(log n) | O(1) | Skip List |
Source: Suryaprakash R.
Source: MCN Professionals
Hieu Tran ([email protected])