Techniques · sudoku

Nice Loops/AICs

An alternating chain of strong and weak links. Whichever end is true, the conclusion holds, so the digit at the marked cell is ruled out.

In the walkthroughs, every Nice Loops/AICs step shades the cells of the pattern and names the cell and digit it proves, so you can see the move on the grid rather than read about it. Press “Skip to next hard step” to jump straight to it.

Worked examples

Puzzles from the books where Nice Loops/AICs is used, those where it is the key technique first. Each link opens the full step-by-step solution.

Extreme Sudoku 1 (147 of 150 puzzles)

• Puzzle 3 · Expert 5 · key technique
• Puzzle 4 · Expert 5 · key technique
• Puzzle 17 · Expert 5 · key technique
• Puzzle 18 · Expert 5 · key technique
• Puzzle 19 · Expert 5 · key technique
• Puzzle 22 · Expert 5 · key technique
• Puzzle 23 · Expert 5 · key technique
• Puzzle 24 · Expert 5 · key technique

Extreme Sudoku 2 (147 of 150 puzzles)

• Puzzle 3 · Expert 5 · key technique
• Puzzle 6 · Expert 5 · key technique
• Puzzle 7 · Expert 5 · key technique
• Puzzle 12 · Expert 6 · key technique
• Puzzle 15 · Expert 5 · key technique
• Puzzle 17 · Expert 5 · key technique
• Puzzle 20 · Expert 5 · key technique
• Puzzle 24 · Expert 6 · key technique

Extreme Sudoku 3 (149 of 150 puzzles)

• Puzzle 8 · Expert 5 · key technique
• Puzzle 12 · Expert 6 · key technique
• Puzzle 13 · Expert 6 · key technique
• Puzzle 17 · Expert 5 · key technique
• Puzzle 21 · Expert 5 · key technique
• Puzzle 23 · Expert 6 · key technique
• Puzzle 24 · Expert 6 · key technique
• Puzzle 26 · Expert 7 · key technique

Where it sits

See the whole ladder on hard sudoku techniques, or look a puzzle up by number under solutions.