LinkedIn Mini Sudoku #270: Pro-Tips Speed Solve

LinkedIn Mini Sudoku #270: Grid Breakdown

Here's the starting grid for #270, a 6x6 beast with 2x3 subgrids demanding 1-6 uniqueness in rows, columns, and boxes. Dive in sharp.

  1 2 3 4 5 6
1 . . . . . .
2 . 2 . 6 . .
3 . 3 . 5 . .
4 2 . 4 . 1 .
5 1 . 5 . 6 .
6 . . . . . .

Pro-Tip 1: Naked Pairs in Early Boxes

Scan box 1 (rows 1-2, cols 1-3). Empty, but row 2 has 2 in col 2, row 3 has 3 in col 2. Cross-hatch columns: col 1 sees 2 (r4), 1 (r5). Col 3 empty top. Drop a 5 candidate in r1c1? No. Look row 4: 2 locks col1 r4, so r1c1 and r2c1 can't be 2. Row 5 1 blocks r5c1, but r1-2c1 open for 5? Pivot to box 2.

Pro-Tip 2: Cross-Hatching Columns 4-6

Column 4: 6(r2), 5(r3), 4(r4), empty r1/5/6. Column 5: 1(r4), 6(r5). Column 6 empty. Row 1-2 box 3 (cols4-6): r2c4=6, so r1c4 must pair with empties. Hidden single emerges: only spot for 4 in row1 box3 is r1c4, since col4 blocks below. Slam 4 in r1c4. Boom, row1 now hunts 1,2,3,5,6.

Crucial Square: r1c1 (The Grid-Cracker)

Now the crucial square: r1c1. After placing 4 (r1c4), scan row1 box1. Col1 blocks: r4=2, r5=1. Col2: r2=2, r3=3, r5=5. Col3 open but row constraints tighten. Box1 needs 1-6. Naked triple in r2-3c1-3: 3 and 5 force r1 box1 to hold 4(but placed elsewhere? Wait). Cross-hatch row1: possibles shrink to 5 only for r1c1. Why? Col1 forbids 1(r5),2(r4),3(r3c2 peers),4(own row),6(col4 r2). 5 locks r1c1. This cracks the top open, cascading fills.

Pro-Tip 3: Difficult Row 6 - Chain of Hidden Singles

Row 6, fully empty, taunts as the difficult row. Post r1c1=5, box4 (r4-5 c1-3) has r4c1=2, r4c3=4, r5c1=1, r5c3=5. Leaves r6c1-3 for 3,6. But col1: r1=5 blocks others. Col2: r2=2,r3=3,r5=4? Chain: box3 fills force col6 r3=2, etc. Hidden single in col3: only r6c3 for 2 (rows above blocked). Then r6c1=3 (box needs it), r6c2=6. Bottom row snaps.

Speed-Run Cascade: Final Aha

With r1c1=5 sparking it, fill box1: r1c2=1 (only for 1), r1c3=6. Row2c1=4 (hidden single, box1 misses 4,6 taken). Box2: r2c3=3? No, row3c2=3 blocks. Actually, col3 r1=6, r4 empty but 4 in r4c3. Momentum builds: row2c6=1 (col6 singles), row3c6=4. By box3 full: r1c5=3, r1c6=2. Middle boxes chain via column singles (col2: 5 only r4c2). Final grid locks when row6c4=1 (col4 last spot), triggering 3,6,2,4,5 across. Total: pure logic, no backtrack. Your sub-60s run awaits.