Complete resources to practice problems solving and prepare for coding interviews. This repo shows my solutions in C# and Python for real interview questions taken from different sites (the origin link to the question is always in the description). Currently, we have a few completed solutions focused on Array, String, Linked List, Stack, Queue, and other data structures.
Please feel free to reference and ⭐ to support this repo, thank you!
- Array
- String
- Linked List
- Hash Table
- Stack
- Queue
- Tree
- Graph
- Bit manipulation
- Sorting
- Compression Algorithms
- Ciphers
- Math
- Dynamic Programming
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Determine if String Halves Are Alike | |
Easy | O(n) | O(1) |
| Determine if Two Strings Are Close | |
Medium | O(n) | O(n) |
| Sort Characters By Frequency | |
Medium | O(n) | O(n) |
| Is Unique | |
Easy | O(n) | O(1) |
| Check Permutation | |
Easy | O(n) | O(1) |
| URLify | |
Easy | O(n) | O(1) |
| Palindrome Permutation | |
Medium | O(n) | O(1) |
| One Way | |
Medium | O(n) | O(n) |
| String Compression | |
Medium | O(n) | O(1) |
| Word Pattern | |
Easy | O(n) | O(n) |
| Detect Capital | |
Easy | O(n) | O(1) |
| Lexicographically Smallest Equivalent String | |
Medium | O(n) | O(n) |
| Flip String to Monotone Increasing |  |
Medium | O(n) | O(1) |
| Permutation in String | |
Medium | O(l_1+(l_2-l_1)) | O(1) |
| Find the Index of the First Occurrence in a String | |
Easy | O(n) | O(1) |
| Custom Sort String | |
Easy | O(n) | O(n) |
| String to Integer (atoi) | |
Medium | O(n) | O(1) |
| Zigzag Conversion | |
Medium | O(n) | O(n) |
| Find the Duplicate Number | |
Medium | O(n log_2 n) | O(1) |
| Length of Last Word | |
Easy | O(n) | O(1) |
| Count and Say | |
Medium | O(n^2) | O(n) |
| Make The String Great | |
Easy | O(n) | O(1) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Middle of the Linked List | |
Easy | O(n) | O(1) |
| Odd Even Linked List | |
Medium | O(n) | O(1) |
| Intersection of Two Linked Lists | |
Easy | O(n) | O(1) |
| Partition List | |
Medium | O(n) | O(1) |
| Swap Nodes in Pairs | |
Medium | O(n) | O(1) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Letter Combinations of a Phone Number | |
Medium | O(n) | O(1) |
| Minimum Rounds to Complete All Tasks | |
Medium | O(n) | O(n) |
| Max Points on a Line | |
Hard | O(n^2) | O(n) |
| Naming a Company | |
Hard | O(n) | O(n) |
| Isomorphic Strings | |
Easy | O(n) | O(n) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Find the Difference | |
Easy | O(n+m) | O(1) |
| Reverse Bits | |
Easy | O(1) | O(1) |
| Add Binary | |
Easy | O(1) | O(1) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| IPO | |
Hard | O(n*log(n)) | O(n) |
| Minimize Deviation in Array | |
Hard | O(nlog(n)) | O(n) |
| Total Cost to Hire K Workers | |
Medium | O((k+2n)*log(2n)) | O(log 2n) |
| Shortest Path to Get All Keys | |
Hard | O(m*n) | O(m*n) |
| Sliding Window Maximum | |
Hard | O(n) | O(k) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Evaluate Reverse Polish Notation | |
Medium | O(n) | O(n) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Majority Element | |
Medium | O(n/2) | O(1) |
| Sort Colors | |
Medium | O(n) | O(1) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Symmetric Tree | |
Easy | O(log n) | O(1) |
| Range Sum of BST | |
Easy | O(n) | O(1) |
| Leaf-Similar Trees | |
Easy | O(n) | O(n) |
| Binary Tree Preorder Traversal | |
Easy | O(n) | O(n) |
| Max Difference Between Node and Ancestor | |
Medium | O(n) | O(1) |
| Max Product of Splitted Binary Tree | |
Medium | O(n) | O(n) |
| Binary Tree Maximum Path Sum | |
Hard | O(n) | O(1) |
| Find if Path Exists in Graph | |
Easy | O(V+E) | O(V) |
| All Paths From Source to Target | |
Medium | O(n) | O(n) |
| Same Tree | |
Easy | O(nlogn) | O(1) |
| Minimum Time to Collect All Apples in a Tree | |
Medium | O(n) | O(n) |
| Number of Nodes in the Sub-Tree With the Same Label | |
Medium | O(n) | O(n) |
| Longest Path With Different Adjacent Characters | |
Hard | O(n) | O(n) |
| Number of Good Paths | |
Hard | O(nlogn) | O(n) |
| Minimum Fuel Cost to Report to the Capital | |
Medium | O(n) | O(n) |
| Construct Quad Tree | |
Medium | O(N^2) | O(N^2) |
| Minimum Absolute Difference in BST | |
Easy | O(N) | O(1) |
| Maximum Level Sum of a Binary Tree | |
Medium | O(N) | O(N) |
| Path Sum | |
Easy | O(log N) | O(1) |
| Balanced Binary Tree | |
Easy | O(log N) | O(1) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Find if Path Exists in Graph | |
Easy | O(V+E) | O(V) |
| KeysAndRooms | |
Medium | O(n) | O(n) |
| Maximal Network Rank | |
Medium | O(V+E) | O(N^2logN) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| LZ77 | |
Medium | O(n) | O(n) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Integer to Roman | |
Medium | O(n) | O(1) |
| Climbing Stairs | |
Medium | O(n) | O(1) |
| Domino and Tromino Tiling | |
Medium | O(n) | O(1) |
| Best Time to Buy and Sell Stock with Cooldown | |
Medium | O(n) | O(1) |
| Count Odd Numbers in an Interval Range | |
Easy | O(1) | O(1) |
| Divide Two Integers | |
Medium | O(log n) | O(1) |
| Title | Solution | Difficulty | Time | Space |
|---|---|---|---|---|
| Longest Common Subsequence | |
Medium | O(m*n) | O(m*n) |
| As Far from Land as Possible | |
Medium | O(m*n) | O(m*n) |
| Edit Distance | |
Hard | O(mn) | O(n) |
| Generate Parentheses | |
Medium | O(n) | O(n) |
| Combination Sum II | |
Medium | O(n) | O(n) |
LeetCode Online is a website containing many algorithm questions. Most of them are real interview questions of Google, Facebook, LinkedIn, Apple, etc.