LinkedIn 6x6 Sudoku #343: Pro-Tips & The Crucial Square

LinkedIn 6x6 Sudoku #343: The Speed-Run Playbook

LinkedIn 6x6 Sudoku #343 cracks open not by brute force, but by spotting the Hidden Single in the top-right 2x3 block. Once you lock that square, the rest of the grid collapses into a clean, logical flow.

Crucial Square: Row 2, Column 2 (The 5)

The grid starts with Row 1 already solved: [1,2,3,4,5,6]. Look at Row 2: [4, null, null, null, null, 3]. The missing numbers are 1, 2, 5, and 6. In the top-right 2x3 block (Rows 1-2, Cols 4-6), we already have 4, 5, 6 in Row 1 and 3 in Row 2. The only spot for 5 in Row 2 is Column 2. Why? Because Column 2 already has a 3 (Row 3) and a 6 (Row 6), and the top-left block needs a 5. This Hidden Single forces the 5 into R2C2, triggering a cascade.

Pro-Tip 1: Cross-Hatching in 2x3 Blocks

In classic 9x9 Sudoku, Cross-Hatching scans rows and columns for a single number. In 6x6, the 2x3 blocks (top-left, top-right, mid-left, mid-right, bottom-left, bottom-right) are your new constraints. For #343, scan the number 6 across the grid. It appears in R1C6, R3C2, R6C2. By drawing invisible lines through Rows 1, 3, 6 and Columns 2, 6, you eliminate 6 from all other cells in those rows/columns. The only remaining spot for 6 in the top-left block is R2C3. This is the Cross-Hatch technique adapted for mini grids.

Pro-Tip 2: The "Only Place" Logic

Row 5 is nearly full: [null, null, 1, 3, null, null]. Missing are 2, 4, 5, 6. Look at Column 3: it has 3, null, 4, 1, null. The 4 is already there. In the bottom-left 2x3 block (Rows 4-6, Cols 1-3), the 4 must go in R4C3? No, R4C3 is 4. Wait, R5C3 is 1. The 4 in the bottom-left block *must* be in R6C1. This is the "Only Place" rule: if a number can only fit in one cell of a block, row, or column, it goes there immediately.

Pro-Tip 3: Scan by Number, Not by Cell

Don't fill cells sequentially. Instead, pick a number like 1 and track it across all six rows. In #343, 1 appears in R1C1, R3C3, R5C3. In the top-left block, 1 is already present. In the mid-left block, 1 is in R5C3. The only spot for 1 in the bottom-left block is R6C1? No, R6C1 is 3. The 1 must go in R4C1. This Number-First Scan reveals forced moves faster than cell-by-cell guessing.

How the Final Answer Cracked

Once R2C2 (the 5) was placed, Row 2 became [4,5,6,2,1,3]. This forced the 1 into R2C5, which eliminated 1 from Column 5 in Rows 3-6. The bottom-right block then had only one spot for 2 (R6C5), which completed the column and unlocked the final row [3,6,5,1,2,4]. The puzzle didn't need a guess; it needed a single Hidden Single to break the symmetry.

Final Veteran Advice

For LinkedIn 6x6 Sudoku #343, remember: Start with the most constrained block (the top-right one), use Cross-Hatching on the 2x3 regions, and scan by number to find your Hidden Singles. Speed comes from seeing the "only place" before your opponent even picks up their pencil.