How To Solve An Expert's Puzzle - Sudoku Handmade Classics #37
Summary
This video demonstrates solving a challenging Sudoku puzzle using Schneider notation, an efficient method for marking potential candidates. The solver systematically works through numbers 1-9, employing techniques like pointing pairs, naked triples, and hidden pairs to deduce cell values. The process highlights how efficient notation can lead to rapid progress and a satisfying solution, offering an alternative to other common Sudoku solving strategies.
Key Insights
Identifying a pointing pair of twos in block 3.
Twos are analyzed. A 'pointing pair' of twos is identified in block 5, as well as in rows 5 and 6. This allows for marking twos in block 3, which are restricted to two specific spots.
Identifying a naked triple in block 6.
A naked triple is found in block 6 involving numbers 3, 6, and 9. These three numbers are confined to three specific cells, which are then marked accordingly. This resolves a six, a three, and a nine.
Sections
Introduction and Puzzle Setup
Introduction to a Sudoku puzzle from Ashish Kumar's book.
The presenter introduces a Sudoku puzzle from the book 'Sudoku Puzzles by Ashish Kumar', thanking the author for permission to feature puzzles. This particular puzzle is number 19 from the classic Sudoku section.
Rationale for using Schneider notation.
The presenter explains that this puzzle is expected to be difficult, necessitating the use of Schneider notation (pencil marks) for efficient solving. While primarily using Schneider, additional marks may be added if needed, with an emphasis on efficiency.
Appreciation for the puzzle's design.
The presenter expresses admiration for the aesthetic design of the puzzle, specifically mentioning the 'swirl' pattern, which was a factor in selecting this particular puzzle to showcase.
Solving with Schneider Notation - Initial Passes
Early solves: Ones in block 9 and column 9.
The solver begins by identifying and placing 'ones'. There's a one in block 9 and column 9, forcing another one. Additional ones are spotted in block 1, column 1, and block 4, leading to several immediate placements.
Identifying a pointing pair of twos in block 3.
Twos are analyzed. A 'pointing pair' of twos is identified in block 5, as well as in rows 5 and 6. This allows for marking twos in block 3, which are restricted to two specific spots.
Locating twos in block 3 and block 6.
More twos are placed. There are two spots for a two in block 3. Twos are also identified in block 6, creating a pointing pair that restricts twos to two specific cells in rows 1 and 2. Additionally, twos in columns 2 and 3 restrict placement in block 1 to two spots.
Analyzing threes and pointing pairs in block 3.
Threes are examined. A pointing pair of threes is found in column 6 and row 3, restricting them to two spots in block 3. This is marked, aiming to solve one of the pair to resolve the other.
Placing fours and identifying a pointing pair in block 1.
Fours are placed by looking at column 7 and row 4, restricting them to two cells. Another pointing pair of fours is identified in block 1, confining them to the top two rows of that block.
Identifying a naked triple in block 6.
A naked triple is found in block 6 involving numbers 3, 6, and 9. These three numbers are confined to three specific cells, which are then marked accordingly. This resolves a six, a three, and a nine.
Utilizing the naked triple to eliminate candidates.
The identified naked triple in block 6 eliminates 3, 6, and 9 from cells in column 2 and blocks 7 and 1, aiding further deductions.
Placing sixes and identifying a pointing pair in block 7.
Sixes are analyzed. They are limited to specific spots in block 6. A pointing pair of sixes is identified in block 7, restricting their placement to two specific cells.
Identifying a hidden/naked pair of threes and sevens.
A pair of threes and sevens is identified in block 3, where these two numbers are restricted to only two specific cells. This is referred to as a hidden pair or naked pair.
Resolving a one and nine pair.
A one and nine pair is found, leading to the immediate solve of a nine in a specific cell. This also resolves another related one.
Placing eights and identifying a pointing pair in block 3.
Eights are placed. There are two spots for an eight in block 5 and three spots in block 6. A pointing pair of eights is identified in block 3, restricting their placement to two specific cells.
Solving a nine through elimination.
A nine is solved. Looking at block 9, there are two spots for a nine. With the previous deductions, one of these becomes solvable as a nine.
Mid-Puzzle Deductions and Naked Triples
Focusing on row 4 for hidden singles.
The solver shifts focus to row 4, which has limited candidates. The missing numbers are 3, 7, 8, and 9. By analyzing existing numbers, an eight is identified and placed.
Solving an eight and its implications.
Solving the eight in row 4 allows for solving another eight. This placement of eights creates a pointing pair in block 3.
Resolving a naked triple in row 4.
Following the placement of the eight, row 4 becomes a naked triple (7, 9 remaining). These are marked to aid further solves.
Identifying an 'eight quad' and a related naked triple.
The placement of eights restricts them to two spots in block 3. Simultaneously, considering numbers 1, 2, 8, 9 in a specific area creates an 'eight quad'. This leads to another naked triple (3, 4, 5) in adjacent cells.
Deriving a two-five naked pair in block 9.
Adjacent to the 3, 4, 5 naked triple, two cells are identified as a naked pair (2, 5), derived from subsequent eliminations.
Solving a five in block 4.
Utilizing the two-five pair and other existing numbers, a five is solved in block 4.
Resolving a naked pair of 4 and 6.
Following the solve of the five, a naked pair of 4 and 6 emerges in adjacent cells. Another related naked pair of 4 and 9 is also identified.
Solving a nine and its immediate chain reactions.
A nine is solved, which triggers the solve of a two and a one-eight pair. This leads to solving another nine, updating a three-six, and resolving a four-six pair.
Advanced Deductions and Puzzle Completion
Solving a naked single six in column 6.
The solver looks at column 6, identifying missing numbers. A naked single six is found and placed, which then allows for placing another six in block 6.
Resolving a two and subsequent number placements.
A two is solved, followed by placing a four and an eight. Cross-hatching with existing eights provides immediate solves for ones and eights.
Placing a three via row 7 analysis.
Row 7 has remaining numbers 3, 4, 5. With existing fours and fives, a three is solved. This leads to placing a four and a five.
Identifying a two and four pair in column 3.
Utilizing Schneider notation, a pair of twos and fours is identified in column 3, creating further restrictions.
Solving a four in column 4.
Analyzing column 4 reveals that a four can only be placed in one spot, thus solving it.
Resolving a naked triple (3, 5, 7) and a four.
A naked triple of 3, 5, and 7 is identified across three cells. Subsequent eliminations resolve a four and other numbers.
Identifying a four-six-seven naked triple.
A naked triple involving 4, 6, and 7 is identified in block 8. This leads to placing a four and a three.
Completing the puzzle with remaining numbers.
The remaining cells are filled by placing sevens, threes, fours, fives, and eights based on the established patterns and notations, finally solving the puzzle.
Conclusion and Reflection
Reflections on using Schneider notation.
The presenter expresses satisfaction with the application of Schneider notation, highlighting its effectiveness in solving the puzzle and showing it as an alternative to other methods like no-mark or full candidate listing.
Call to action and future content.
The presenter asks viewers for feedback on the solving method and encourages them to return for daily Sudoku puzzles in February. A reminder to like, share, and subscribe is given.
Ask a Question
*Uses 1 Wisdom coin from your coin balance
