36. Valid Sudoku

Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: 1. Each row must contain the digits 1-9 without repetition. 2. Each column must contain the digits 1-9 without repetition. 3. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition. Note: A Sudoku board (partially filled) could be valid but is not necessarily solvable. Only the filled cells need to be validated.

🧠 Visual Learning Aid

💡 Approach

• → Use sets for rows, columns, and 3x3 boxes
• → Box index = (row/3) * 3 + (col/3)
• → Check for duplicates as we iterate through board
• → Time: O(n²), Space: O(n²) where n = 9

🧭 Prerequisites

🛠️ Hints & Pitfalls

Hints

• •Use sets for rows, columns, and 3x3 boxes
• •Box index = (row/3) * 3 + (col/3)
• •Check for duplicates as we iterate through board

Common Pitfalls

• •Time: O(n²), Space: O(n²) where n = 9

🧪 Test Cases

🔗 Related Problems