https://github.com/soroush-04/algorithms-data-structures

https://github.com/soroush-04/algorithms-data-structures

algorithms data-structures python

Last synced: about 2 months ago
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• Host: GitHub
• URL: https://github.com/soroush-04/algorithms-data-structures
• Owner: soroush-04
• Created: 2024-09-19T15:03:30.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2025-05-18T02:31:20.000Z (about 1 year ago)
• Last Synced: 2025-05-18T02:47:35.114Z (about 1 year ago)
• Topics: algorithms, data-structures, python
• Language: Python
• Homepage:
• Size: 78.1 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

          
# Algorithms and Data Structures Practice in Python

## Favorite Problems

- **Mushroom Picker**

  - Technique: Prefix Sums, Two Pointers | [Code Link](https://github.com/soroush-04/Algorithms-DS/commit/30a49e17b09a87c77d69216f6834c818f520a6ca)

- **Genomic Range Query**

  - Technique: Prefix Sums, Two Pointers, Sliding Window | [Code Link](https://github.com/soroush-04/Algorithms-DS/commit/a0d98aaf3dd05eae152d93a32d31836036871d7c)

- **Graph Valid Tree**

  - Technique: DFS, Cycle Checking, Connectivity Check | [Code Link](https://github.com/soroush-04/Algorithms-DS/commit/ea384f78d6560cc8b4b2e4e3a89144e57ce9c166)

- **N-Queens**

  - Technique: Backtracking | [Code Link](https://github.com/soroush-04/Algorithms-DS/blob/main/favorites/n_queens.py)

- **Top K Frequent Elements**

  - Technique: Bucket Sort | [Code Link](https://github.com/soroush-04/Algorithms-DS/blob/main/favorites/top_k_frequency.py)

- **Counting Bits**

  - Technique: Bit Manipulation, Dynamic Programming | [Code Link](https://github.com/soroush-04/Algorithms-DS/blob/main/favorites/counting_bits.py)

- **Subtree of Another Tree**

  - Technique: Tree Traversal, Recursion | [Code Link](https://github.com/soroush-04/Algorithms-DS/blob/main/favorites/subtree.py)

- **Balanced Binary Tree**

  - Technique: DFS, Height Calculation | [Code Link](https://github.com/soroush-04/Algorithms-DS/blob/main/favorites/balanced_binary_tree.py)

- **Letter Combinations of a Phone Number**

  - Technique: backtracking, string join | [Code Link](https://github.com/soroush-04/Algorithms-DS/blob/main/favorites/letters_phone_numer.py)

- **Permutations**

  - Technique: backtracking | [Code Link](https://github.com/soroush-04/Algorithms-DS/blob/main/favorites/permutations.py)

- **Equal Row and Column Pairs**

  - Technique: Hashmaps, Tuples, Matrix | [Code Link](https://github.com/soroush-04/Algorithms-DS/blob/main/favorites/equal_pairs.py)

## Common mistakes

### Slicing 

- A[-K:]: This slice retrieves the last K elements from the list, starting from the K-th element from the end.

- A[:-K]: This slice retrieves all elements from the beginning of the list up to (but not including) the last K elements.

  - Sample problem: cyclic rotation

### Set()

- Whenever we only care about uniqueness and a single occurence, consider using sets.

- Converting the list to a set allows O(1) average time complexity for membership checks.

### Sliding Window

- Consider using this technique when searching for specific subarrays or contiguous sequences.

### Hashmaps

- Use tuples as keys if needed not the list.

### Stack

- You need to perform on current and previous index? Consider using stack for optimized performance. 

### Sorting

- Merge Sort has guaranteed O(n log n) time complexity, which can be preferable when the worst case is a concern.

### Bucket Sort

- Optimize the time complexity to O(N).

- It is a 2D array,

- We kinda try to swap and redesign the key-values of frequency hashmap.

### Trees

- In BST do not traverse the wrong subtree!

- Don't forget to propagate the state of unbalanced subtrees up the tree.

### BFS

- Consider using it for shortest path in unweighted graphs.

### DFS

- Consider using it for backtracking scenarios.

### Nested Data

- **Hashmaps**: Use `.items()` to iterate through key-value pairs and use the value to move one layer inward. 

- **Lists**: Use `item in items` to move one layer inward.

### Backtracking

- Don’t forget to undo (backtrack) changes after recursive calls.

- Recursion base case must be created accuractely.

- Don't forget to call the backtracking function at the end!

- Each for loop in a recursive callback function has its separate own state.

### Dynamic Programming

- Check for fibonnaci patterns

### Bit Manipulation

- Logical and returns the first falsy value or the last value if all are truthy.

- Logical or returns the first truthy value.

- XOR: like a toggle switch to add/remove features. Also keep in mind XOR of two same numbers is zero.

- Check LSB (least significant bit) with 'i & 1'  or 'i % 2'