Sum or Difference Sudoku (Fun With Sudoku #136)

Welcome to a puzzle that will keep you guessing about the nature of its clues! This Sum or Difference Sudoku is the second of two puzzles I created to practice for the World Sudoku Championship 2015, and I believe it's even better than the first puzzle, which was published with the title Sum or Difference Sudoku (Daily Sudoku League #140). The puzzle uses a classic 9x9 grid, but with an additional layer of logic that comes from clues placed outside the grid. The core idea is that each external clue represents either the sum or the difference of the two nearest digits in that row or column. The clever design of this puzzle makes it difficult to guess which operation applies to a given clue, adding a rich layer of deduction.

This puzzle is a great way to experience a championship-level variant that requires flexible thinking. The ambiguity of the clues forces you to consider multiple possibilities and use classic Sudoku logic to determine the correct path. It's perfect for a focused session where you can explore the intricate interplay between the sum/difference rule and the grid. Enjoy this well-crafted and challenging puzzle.

This Sum or Difference Sudoku I am posting as the 136th Sudoku in the Fun With Sudoku Series. Can you solve this Sudoku puzzle variation?

Rules of Sum or Difference Sudoku

Standard Classic Sudoku Rules apply. Additionally, the clue outside the grid indicates either the sum or the difference of the two nearest digits in the corresponding column or row.