| 1 |
Two Sum |
|
|
Easy |
O(nlogn) |
O(1) |
Array, Hash Table |
| 2 |
Add Two Numbers |
|
|
Medium |
O(max(m,n)) |
O(1) |
Linked List, Math, Recursion |
| 5 |
Longest Palindromic Substring |
|
|
Medium |
O(n2) |
O(n2) |
String, DP |
| 20 |
Valid Parentheses |
|
|
Easy |
O(n) |
O(n) |
String, Stack |
| 21 |
Merge Two Sorted Lists |
|
|
Easy |
O(n) |
O(n) |
Linked List, Recursion |
| 23 |
Merge K Sorted Lists |
|
|
Hard |
O(nlogk) |
O(n) |
Linked List, Divide And Conquer, Priority Queue, Merge Sort |
| 42 |
Trapping Rain Water |
|
|
Hard |
O(n) |
O(1) |
Array, Two Pointers, DP, Stack |
| 127 |
Word Ladder |
|
|
Hard |
O(nm2) |
O(nm) |
BFS, Hash Table, String |
| 138 |
Copy List With Random Pointers |
|
|
Medium |
O(n) |
O(1) |
Hash Table, Linked List |
| 146 |
LRU Cache |
|
|
Medium |
O(1) |
O(1) |
Hash Table, Linked List, Design, Doubly Linked List |
| 200 |
Number Of Islands |
|
|
Medium |
O(mn) |
O(min(m,n)) |
Array, BFS, DFS, Matrix, Union Find |
| 295 |
Find Median From Data Stream |
|
|
Hard |
O(logn) |
O(n) |
Two Pointers, Design, Sorting, Priority Queue, Data Stream |
| 297 |
Serialize And Deserialize Binary Tree |
|
|
Hard |
O(n) |
O(n) |
String, Tree, Dfs, Bfs, Design, Binary Tree |
| 692 |
Top K Frequent Words |
|
|
Medium |
O(nlogn) |
O(n) |
Hash Table, String, Trie, Sorting, Priority Queue, Bucket Sort, Counting |
| 763 |
Partition Labels |
|
|
Medium |
O(n) |
O(n) |
Hash Table, Two Pointers, String, Greedy |
| 819 |
Most Common Word |
|
|
Easy |
O(n+m) |
O(n+m) |
Hash Table, String |
| 937 |
Reorder Data In Log Files |
|
|
Easy |
O(nlogn) |
O(n) |
Array, String, Sorting |
| 973 |
K Closest Points To Origin |
|
|
Medium |
O(nlogn) |
O(n) |
Array, Math, Divide And Conquer, Geometry, Sorting, Priority Queue, Quick Select |
| 994 |
Rotting Oranges |
|
|
Medium |
O(mn) |
O(mn) |
Array, BFS, Matrix |
| 1192 |
Critical Connections In A Network |
|
|
Hard |
O(E+V) |
O(E+V) |
DFS, Graph, Biconnected Components |