Sudoku solver

A lightweight, readable Sudoku solver that recursively calls itself

• Repeatedly places forced digits (unique in row/col/box).
• Then branches on the digit with the fewest possible placements to minimize search and recursively calls itself again.
• Tracks tried (row, col, digit) guesses/branches to avoid recounting the same solution.
• Returns a solution (if exists) and whether the puzzle is underconstraind, overconstrained or unique.

Quick start

Run the main script sudoku_main.