Khoan Vokhac

Quick and detailed solutions of ultra sudoku Khoan Vokhac

The 500 puzzles in Ultra Sudoku are excellent exercices for every player. Stephane Lepage gives two rules, named here single putting and single posting. They are sufficient for finishing 450 puzzles; but other rules are necessary for the 50 other puzzles. Chapter 1 finishes 361 puzzles with single putting rule. Chapter 2 finishes 89 puzzles with single posting rule. Chapter 3 finishes 34 puzzles with multiple putting rule. Chapter 4 finishes 13 puzzles with covering technique. Chapter 5 uses perfect rectangles to prove that puzzle 134 and puzzle 203 have many solutions. Chapter 6 studies the difficult puzzle 391.