Step-by-step solution
Steps 65
Estimated time 104 – 156 min
Hardest technique X-Wing
Clues 23
Given digit (clue)
Solved digit
Placement (✓ RlCc=d)
Elimination (✗ RlCc≠d)
Look at cell R5C4.
Every other digit already appears in its row, column or box.
Only one option remains: R5C4 = 2.
Look at cell R4C4.
Every other digit already appears in its row, column or box.
Only one option remains: R4C4 = 3.
Look at cell R6C5.
Every other digit already appears in its row, column or box.
Only one option remains: R6C5 = 9.
Look at cell R6C6.
Every other digit already appears in its row, column or box.
Only one option remains: R6C6 = 4.
Scan the empty cells in this box where 1 could go.
Across the whole box, 1 has only one possible spot left.
So R1C5 = 1.
Scan the empty cells in this row where 5 could go.
Across the whole row, 5 has only one possible spot left.
So R2C5 = 5.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R3C4 = 8.
Scan the empty cells in this box where 7 could go.
Across the whole box, 7 has only one possible spot left.
So R3C5 = 7.
Scan the empty cells in this column where 5 could go.
Across the whole column, 5 has only one possible spot left.
So R3C7 = 5.
Scan the empty cells in this row where 1 could go.
Across the whole row, 1 has only one possible spot left.
So R4C1 = 1.
Scan the empty cells in this row where 5 could go.
Across the whole row, 5 has only one possible spot left.
So R5C3 = 5.
Scan the empty cells in this box where 7 could go.
Across the whole box, 7 has only one possible spot left.
So R5C7 = 7.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R6C7 = 3.
Scan the empty cells in this row where 6 could go.
Across the whole row, 6 has only one possible spot left.
So R6C8 = 6.
Scan the empty cells in this row where 1 could go.
Across the whole row, 1 has only one possible spot left.
So R9C4 = 1.
Look at cell R2C4.
Every other digit already appears in its row, column or box.
Only one option remains: R2C4 = 6.
Scan the empty cells in this row where 6 could go.
Across the whole row, 6 has only one possible spot left.
So R1C1 = 6.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R1C3 = 8.
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R3C1 = 9.
Scan the empty cells in this column where 6 could go.
Across the whole column, 6 has only one possible spot left.
So R3C9 = 6.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R6C2 = 8.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R7C1 = 8.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R7C6 = 6.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R8C2 = 6.
Scan the empty cells in this column where 1 could go.
Across the whole column, 1 has only one possible spot left.
So R8C7 = 1.
Scan the empty cells in this column where 7 could go.
Across the whole column, 7 has only one possible spot left.
So R2C2 = 7.
(1) Spot R1C6 and R3C6 on this column. (2) Spot R6C1 and R6C3 in this box. (3) Spot R7C5 and R8C5 in this box.
(1) These two cells can only hold 2 and 3: they reserve those digits. (2) These two cells can only hold 2 and 7: they reserve those digits. (3) These two cells can only hold 2 and 3: they reserve those digits.
(1) 2 and 3 are therefore removed from the other cells of the column. (2) 2 and 7 are therefore removed from the other cells of the box. (3) 2 and 3 are therefore removed from the other cells of the box.
Spot R4C2 and R5C2 on this column.
These two cells can only hold 4 and 9: they reserve those digits.
4 and 9 are therefore removed from the other cells of the column.
Spot R3C2 and R3C6 on this row.
These two cells can only hold 2 and 3: they reserve those digits.
2 and 3 are therefore removed from the other cells of the row.
Look at where 9 can go on this column.
All its spots lie within a single box (R4C9 and R5C9).
9 is therefore removed from the rest of the box.
Find 4 on one row and one column, each with two candidate positions, sharing a box.
The two strands meet in the shared box. One of the two free ends must hold 4.
R8C8 is seen by both free ends: 4 is therefore eliminated there.
Spot R8C5 and R8C8 on this row.
These two cells can only hold 2 and 3: they reserve those digits.
2 and 3 are therefore removed from the other cells of the row.
Find 3 on two rows, each with exactly two candidate positions.
A shared column connects one end of each pair. Whichever way the logic falls, one of the two free ends must hold 3.
R2C3 is seen by both free ends: 3 is therefore eliminated there.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R1C6 = 3.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R3C2 = 3.
Scan the empty cells in this column where 3 could go.
Across the whole column, 3 has only one possible spot left.
So R7C3 = 3.
Scan the empty cells in this box where 2 could go.
Across the whole box, 2 has only one possible spot left.
So R7C5 = 2.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R8C5 = 3.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R8C9 = 8.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R9C9 = 3.
Look at cell R3C6.
Every other digit already appears in its row, column or box.
Only one option remains: R3C6 = 2.
Look at cell R8C6.
Every other digit already appears in its row, column or box.
Only one option remains: R8C6 = 5.
Look at cell R8C8.
Every other digit already appears in its row, column or box.
Only one option remains: R8C8 = 2.
Look at cell R9C2.
Every other digit already appears in its row, column or box.
Only one option remains: R9C2 = 2.
Look at cell R9C6.
Every other digit already appears in its row, column or box.
Only one option remains: R9C6 = 8.
Look at cell R1C8.
Every other digit already appears in its row, column or box.
Only one option remains: R1C8 = 9.
Look at cell R7C8.
Every other digit already appears in its row, column or box.
Only one option remains: R7C8 = 4.
Look at cell R9C1.
Every other digit already appears in its row, column or box.
Only one option remains: R9C1 = 5.
Look at cell R1C7.
Every other digit already appears in its row, column or box.
Only one option remains: R1C7 = 2.
Look at cell R2C9.
Every other digit already appears in its row, column or box.
Only one option remains: R2C9 = 4.
Look at cell R3C8.
Every other digit already appears in its row, column or box.
Only one option remains: R3C8 = 1.
Look at cell R4C7.
Every other digit already appears in its row, column or box.
Only one option remains: R4C7 = 4.
Look at cell R5C9.
Every other digit already appears in its row, column or box.
Only one option remains: R5C9 = 9.
Look at cell R7C7.
Every other digit already appears in its row, column or box.
Only one option remains: R7C7 = 9.
Look at cell R2C1.
Every other digit already appears in its row, column or box.
Only one option remains: R2C1 = 2.
Look at cell R2C3.
Every other digit already appears in its row, column or box.
Only one option remains: R2C3 = 1.
Look at cell R2C8.
Every other digit already appears in its row, column or box.
Only one option remains: R2C8 = 3.
Look at cell R3C3.
Every other digit already appears in its row, column or box.
Only one option remains: R3C3 = 4.
Look at cell R4C2.
Every other digit already appears in its row, column or box.
Only one option remains: R4C2 = 9.
Look at cell R4C9.
Every other digit already appears in its row, column or box.
Only one option remains: R4C9 = 2.
Look at cell R5C2.
Every other digit already appears in its row, column or box.
Only one option remains: R5C2 = 4.
Look at cell R6C1.
Every other digit already appears in its row, column or box.
Only one option remains: R6C1 = 7.
Look at cell R6C3.
Every other digit already appears in its row, column or box.
Only one option remains: R6C3 = 2.
Look at cell R8C1.
Every other digit already appears in its row, column or box.
Only one option remains: R8C1 = 4.
Look at cell R8C3.
Every other digit already appears in its row, column or box.
Only one option remains: R8C3 = 7.