LeetCode 36: Valid Sudoku | Python Solution | Hash Sets Approach

In this tutorial, I'll show you how to determine if a 9x9 Sudoku board is valid using #python and #hashsets. We'll validate rows, columns, and 3x3 sub-boxes efficiently with a single pass solution. ⏱️ **Time Complexity:** O(1) - We're always checking exactly 81 cells 🗂️ **Space Complexity:** O(1) - We use constant extra space ## 📍 Timestamps 00:00 - Understanding problem statement 00:47 - Whiteboarding 02:10 - Dry-run 04:10 - Big O Notation explained 05:07 - Python code walk-through 06:17 - Solution analysis - runtime + memory ## 🧠 Key Concepts - Hash Sets - Matrix Traversal - Input Validation - Efficient Constraint Checking ## 💡 Learning Points - Using hash sets to track seen elements - Handling 2D array traversal efficiently - Mathematically mapping grid positions to sub-boxes - Avoiding unnecessary iterations ## 🔗 Related Problems - LeetCode 37: Sudoku Solver - LeetCode 73: Set Matrix Zeroes - LeetCode 348: Design Tic-Tac-Toe - LeetCode 1074: Number of Submatrices That Sum to Target ## 👥 Target Audience This video is perfect for software engineering interview candidates, computer science students, and developers looking to improve their problem-solving skills with #datastructures and #algorithms. ## 📚 Prerequisites - Basic Python knowledge - Understanding of hash sets - Familiarity with 2D arrays/matrices ## 🔗 Links - LeetCode problem: https://leetcode.com/problems/valid-sudoku/ - Solution code: https://leetcode.com/problems/valid-sudoku/solutions/6972766/hash-set-validation-solution-in-python-w-exi2 ## 💬 Call-to-Action If you found this solution helpful, please hit that subscribe button and notification bell to support the channel! Have questions or alternative approaches? Share them in the comments below! ## 💡 Additional Tips - Emphasize the elegant single-pass approach rather than checking rules separately - Explain clearly how to map grid positions to the nine 3x3 sub-boxes - Show a visual example of the hash set checking process