Sudoku Solver (Advanced)

Performance at Scale

While basic backtracking works for $9 \times 9$ Sudoku, larger puzzles or high-volume solvers require better state management.

Bitmask Optimization

Instead of checking rows and columns using loops ($O(N)$), we use a single bitmask for each row, column, and box. Checking for a conflict becomes a single bitwise AND operation ($O(1)$).