LinkedIn Mini Sudoku #198: Solve Cornering

The Cornering puzzle presents a 6x6 grid with strategic clues placed primarily in the corners and edges. This puzzle is an excellent opportunity to practice corner pattern recognition, a proven technique for mini Sudoku solving.

Initial Setup

Your starting grid has these prefilled cells:

• Top-left corner: 1, 2, 3 in the first row
• Second row: 4, 5 in the first two positions
• Third row: 6 in the first position
• Bottom-right corner: 6, 5, 1 in the last row
• Middle area: 2 in row 4, column 6
• Bottom-middle: 3, 4 in row 5, columns 5-6

Step-by-Step Solution Strategy

Step 1: Solve the Top-Left 2x3 Box

The top-left box already contains 1, 2, 3, 4, 5. Only 6 is missing, and it must go in row 3, column 2.

Step 2: Complete Row 1 Using Column Constraints

Row 1 has 1, 2, 3 and needs 4, 5, 6. Look at column 4: it already has 6 in row 6. Therefore, row 1, column 4 cannot be 6. Analyze the top-right box constraints to determine that row 1, column 4 = 5.

This forces row 1, column 5 = 4 and row 1, column 6 = 6.

Step 3: Apply Box-Line Reduction on Row 2

Row 2 contains 4, 5 and needs 1, 2, 3, 6. The top-middle box (rows 1-3, columns 4-6) now has 5, 4, 6 from row 1. It needs 1, 2, 3.

Row 2, column 4 must be one of these missing numbers. By checking row 2's column constraints, row 2, column 4 = 1, row 2, column 5 = 2, and row 2, column 6 = 3.

Step 4: Complete Row 3 Using Box Constraints

Row 3 has 6 in column 1. The top-left box now has 1, 2, 3, 4, 5, 6 (complete). The top-middle box needs the remaining numbers. Row 3 needs 2, 3, 4, 5. By elimination and checking columns 4, 5, 6, you'll place: row 3, column 2 = 4, row 3, column 3 = 2, row 3, column 4 = 3, row 3, column 5 = 1, row 3, column 6 = 5.

Step 5: Solve the Bottom-Right Box First

The bottom-right 2x3 box (rows 5-6, columns 4-6) already has 6, 5, 1 in row 6, and 3, 4 in row 5. It needs 2 for row 5, column 4. Therefore, row 5, column 4 = 2.

Step 6: Use Column Scanning for Rows 4-5

Column 6 now has 6, 3, 5, 2, 4, 1. Row 4, column 6 must fit row 4's remaining numbers. Work through columns 1-5 for rows 4-5 using the elimination technique.

For row 4: Column constraints show row 4, column 1 = 3, row 4, column 2 = 1, row 4, column 3 = 5, row 4, column 4 = 4, row 4, column 5 = 6.

Step 7: Complete Row 5 and Row 6

With most cells filled, row 5 becomes straightforward. By checking remaining candidates in each column: row 5, column 1 = 5, row 5, column 2 = 6, row 5, column 3 = 1.

Row 6, column 1 = 2, row 6, column 2 = 3, row 6, column 3 = 4.

Key Techniques Used

• Naked Singles: Cells where only one number can fit
• Corner Patterns: Corners revealed crucial starting points for solving
• Box-Line Reduction: Eliminating candidates by analyzing box and row/column intersections
• Column and Row Elimination: Systematically removing impossible candidates

Practice Tip

The Cornering puzzle teaches you to recognize how strategically placed clues in corners accelerate solving. Always start with the most constrained regions (boxes and rows with the most filled cells) before moving to sparse areas.