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)
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R2C4 = 9.
Scan the empty cells in this column where 6 could go.
Across the whole column, 6 has only one possible spot left.
So R3C1 = 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 box where 4 could go.
Across the whole box, 4 has only one possible spot left.
So R9C2 = 4.
Scan the empty cells in this row where 2 could go.
Across the whole row, 2 has only one possible spot left.
So R9C9 = 2.
Look at cell R9C4.
Every other digit already appears in its row, column or box.
Only one option remains: R9C4 = 3.
Look at cell R7C4.
Every other digit already appears in its row, column or box.
Only one option remains: R7C4 = 4.
Look at cell R7C7.
Every other digit already appears in its row, column or box.
Only one option remains: R7C7 = 6.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R4C5 = 5.
Scan the empty cells in this column where 4 could go.
Across the whole column, 4 has only one possible spot left.
So R6C6 = 4.
Scan the empty cells in this row where 3 could go.
Across the whole row, 3 has only one possible spot left.
So R7C3 = 3.
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R7C5 = 9.
Scan the empty cells in this box where 1 could go.
Across the whole box, 1 has only one possible spot left.
So R8C5 = 1.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R8C6 = 5.
Look at cell R5C5.
Every other digit already appears in its row, column or box.
Only one option remains: R5C5 = 8.
Look at cell R8C3.
Every other digit already appears in its row, column or box.
Only one option remains: R8C3 = 9.
Scan the empty cells in this row where 9 could go.
Across the whole row, 9 has only one possible spot left.
So R1C2 = 9.
Scan the empty cells in this box where 2 could go.
Across the whole box, 2 has only one possible spot left.
So R1C3 = 2.
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R5C9 = 9.
Scan the empty cells in this column where 9 could go.
Across the whole column, 9 has only one possible spot left.
So R6C1 = 9.
Scan the empty cells in this row where 9 could go.
Across the whole row, 9 has only one possible spot left.
So R9C8 = 9.
Scan the empty cells in this row where 3 could go.
Across the whole row, 3 has only one possible spot left.
So R5C2 = 3.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R1C9 = 6.
Scan the empty cells in this row where 2 could go.
Across the whole row, 2 has only one possible spot left.
So R5C4 = 2.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R5C8 = 6.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R6C4 = 6.
(1) Spot R1C6 and R5C6 on this column. (2) Spot R1C6 and R3C4 in this box.
(1) These two cells can only hold 1 and 7: they reserve those digits. (2) These two cells can only hold 1 and 7: they reserve those digits.
(1) 1 and 7 are therefore removed from the other cells of the column. (2) 1 and 7 are therefore removed from the other cells of the box.
Find 7 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 7.
R3C3 is seen by both free ends: 7 is therefore eliminated there.
Scan the empty cells in this box where 7 could go.
Across the whole box, 7 has only one possible spot left.
So R2C1 = 7.
Look at cell R2C7.
Every other digit already appears in its row, column or box.
Only one option remains: R2C7 = 3.
Look at cell R4C1.
Every other digit already appears in its row, column or box.
Only one option remains: R4C1 = 8.
Look at cell R9C1.
Every other digit already appears in its row, column or box.
Only one option remains: R9C1 = 5.
Look at cell R9C3.
Every other digit already appears in its row, column or box.
Only one option remains: R9C3 = 8.
Look at cell R2C6.
Every other digit already appears in its row, column or box.
Only one option remains: R2C6 = 8.
Look at cell R3C6.
Every other digit already appears in its row, column or box.
Only one option remains: R3C6 = 3.
Scan the empty cells in this row where 8 could go.
Across the whole row, 8 has only one possible spot left.
So R3C2 = 8.
Scan the empty cells in this row where 3 could go.
Across the whole row, 3 has only one possible spot left.
So R4C9 = 3.
Find 1 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 1.
R4C8 is seen by both free ends: 1 is therefore eliminated there.
Find where 1 and 8 can go in this box.
These two digits only fit in R6C8 and R6C9 in the box.
The other candidates in R6C8 and R6C9 are therefore eliminated.
Spot R6C8 and R6C9 on this row.
These two cells can only hold 1 and 8: they reserve those digits.
1 and 8 are therefore removed from the other cells of the row.
Find where 4 and 7 can go on this column.
These two digits only fit in R3C9 and R8C9 on the column.
The other candidates in R3C9 and R8C9 are therefore eliminated.
Find 1 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 1.
R3C3 is seen by both free ends: 1 is therefore eliminated there.
Look at cell R3C3.
Every other digit already appears in its row, column or box.
Only one option remains: R3C3 = 5.
Look at cell R6C3.
Every other digit already appears in its row, column or box.
Only one option remains: R6C3 = 7.
Look at cell R6C7.
Every other digit already appears in its row, column or box.
Only one option remains: R6C7 = 2.
Look at cell R2C2.
Every other digit already appears in its row, column or box.
Only one option remains: R2C2 = 1.
Look at cell R2C9.
Every other digit already appears in its row, column or box.
Only one option remains: R2C9 = 5.
Look at cell R4C2.
Every other digit already appears in its row, column or box.
Only one option remains: R4C2 = 2.
Look at cell R5C3.
Every other digit already appears in its row, column or box.
Only one option remains: R5C3 = 1.
Look at cell R5C6.
Every other digit already appears in its row, column or box.
Only one option remains: R5C6 = 7.
Look at cell R6C2.
Every other digit already appears in its row, column or box.
Only one option remains: R6C2 = 5.
Look at cell R7C9.
Every other digit already appears in its row, column or box.
Only one option remains: R7C9 = 8.
Look at cell R1C6.
Every other digit already appears in its row, column or box.
Only one option remains: R1C6 = 1.
Look at cell R1C8.
Every other digit already appears in its row, column or box.
Only one option remains: R1C8 = 7.
Look at cell R3C4.
Every other digit already appears in its row, column or box.
Only one option remains: R3C4 = 7.
Look at cell R3C9.
Every other digit already appears in its row, column or box.
Only one option remains: R3C9 = 4.
Look at cell R4C4.
Every other digit already appears in its row, column or box.
Only one option remains: R4C4 = 1.
Look at cell R4C8.
Every other digit already appears in its row, column or box.
Only one option remains: R4C8 = 4.
Look at cell R6C9.
Every other digit already appears in its row, column or box.
Only one option remains: R6C9 = 1.
Look at cell R7C8.
Every other digit already appears in its row, column or box.
Only one option remains: R7C8 = 5.
Look at cell R8C9.
Every other digit already appears in its row, column or box.
Only one option remains: R8C9 = 7.
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 = 7.
Look at cell R6C8.
Every other digit already appears in its row, column or box.
Only one option remains: R6C8 = 8.
Look at cell R8C7.
Every other digit already appears in its row, column or box.
Only one option remains: R8C7 = 4.