Step-by-step solution
Steps 65
Estimated time 104 – 156 min
Hardest technique X-Wing
Clues 22
Given digit (clue)
Solved digit
Placement (✓ RlCc=d)
Elimination (✗ RlCc≠d)
Look at cell R1C5.
Every other digit already appears in its row, column or box.
Only one option remains: R1C5 = 3.
Look at cell R9C5.
Every other digit already appears in its row, column or box.
Only one option remains: R9C5 = 5.
Scan the empty cells in this box where 7 could go.
Across the whole box, 7 has only one possible spot left.
So R1C6 = 7.
Scan the empty cells in this row where 5 could go.
Across the whole row, 5 has only one possible spot left.
So R1C7 = 5.
Scan the empty cells in this row where 3 could go.
Across the whole row, 3 has only one possible spot left.
So R2C2 = 3.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R2C7 = 8.
Scan the empty cells in this box where 7 could go.
Across the whole box, 7 has only one possible spot left.
So R3C8 = 7.
Scan the empty cells in this box where 2 could go.
Across the whole box, 2 has only one possible spot left.
So R3C9 = 2.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R4C2 = 6.
Scan the empty cells in this column where 2 could go.
Across the whole column, 2 has only one possible spot left.
So R4C3 = 2.
Scan the empty cells in this column where 5 could go.
Across the whole column, 5 has only one possible spot left.
So R4C8 = 5.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R5C6 = 5.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R6C2 = 5.
Scan the empty cells in this row where 2 could go.
Across the whole row, 2 has only one possible spot left.
So R6C4 = 2.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R6C7 = 6.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R7C3 = 5.
(1) Find where 2 and 7 can go on this column. (2) Find where 2 and 7 can go in this box.
(1) These two digits only fit in R7C7 and R8C7 on the column. (2) These two digits only fit in R7C7 and R8C7 in the box.
(1) The other candidates in R7C7 and R8C7 are therefore eliminated. (2) The other candidates in R7C7 and R8C7 are therefore eliminated.
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R2C5 = 9.
Scan the empty cells in this box where 2 could go.
Across the whole box, 2 has only one possible spot left.
So R2C6 = 2.
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 7 could go.
Across the whole box, 7 has only one possible spot left.
So R7C7 = 7.
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R7C9 = 9.
Scan the empty cells in this row where 9 could go.
Across the whole row, 9 has only one possible spot left.
So R8C4 = 9.
Scan the empty cells in this box where 2 could go.
Across the whole box, 2 has only one possible spot left.
So R8C7 = 2.
Scan the empty cells in this column where 7 could go.
Across the whole column, 7 has only one possible spot left.
So R5C1 = 7.
Scan the empty cells in this row where 7 could go.
Across the whole row, 7 has only one possible spot left.
So R8C2 = 7.
Scan the empty cells in this column where 8 could go.
Across the whole column, 8 has only one possible spot left.
So R9C9 = 8.
Spot R9C2 and R9C7 on this row.
These two cells can only hold 1 and 4: they reserve those digits.
1 and 4 are therefore removed from the other cells of the row.
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.
R5C4 is seen by both free ends: 4 is therefore eliminated there.
Look at where 4 can go in this box.
All its spots lie on a single row (R4C4 and R4C6).
4 is therefore removed from that row outside the box.
Look at cell R4C7.
Every other digit already appears in its row, column or box.
Only one option remains: R4C7 = 9.
Scan the empty cells in this column where 9 could go.
Across the whole column, 9 has only one possible spot left.
So R3C1 = 9.
Scan the empty cells in this row where 9 could go.
Across the whole row, 9 has only one possible spot left.
So R5C2 = 9.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R7C2 = 8.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R8C6 = 8.
Look at where 1 can go in this box.
All its spots lie on a single row (R7C4 and R7C6).
1 is therefore removed from that row outside the box.
Find 4 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 4.
R1C9 is seen by both free ends: 4 is therefore eliminated there.
Look at cell R1C9.
Every other digit already appears in its row, column or box.
Only one option remains: R1C9 = 1.
Look at cell R2C8.
Every other digit already appears in its row, column or box.
Only one option remains: R2C8 = 4.
Look at cell R6C9.
Every other digit already appears in its row, column or box.
Only one option remains: R6C9 = 3.
Look at cell R2C4.
Every other digit already appears in its row, column or box.
Only one option remains: R2C4 = 1.
Look at cell R5C9.
Every other digit already appears in its row, column or box.
Only one option remains: R5C9 = 4.
Look at cell R6C1.
Every other digit already appears in its row, column or box.
Only one option remains: R6C1 = 1.
Look at cell R5C7.
Every other digit already appears in its row, column or box.
Only one option remains: R5C7 = 1.
Look at cell R9C7.
Every other digit already appears in its row, column or box.
Only one option remains: R9C7 = 4.
Look at cell R9C2.
Every other digit already appears in its row, column or box.
Only one option remains: R9C2 = 1.
Look at cell R3C2.
Every other digit already appears in its row, column or box.
Only one option remains: R3C2 = 4.
Look at cell R3C6.
Every other digit already appears in its row, column or box.
Only one option remains: R3C6 = 6.
Look at cell R8C3.
Every other digit already appears in its row, column or box.
Only one option remains: R8C3 = 3.
Look at cell R8C8.
Every other digit already appears in its row, column or box.
Only one option remains: R8C8 = 1.
Look at cell R9C6.
Every other digit already appears in its row, column or box.
Only one option remains: R9C6 = 3.
Look at cell R9C8.
Every other digit already appears in its row, column or box.
Only one option remains: R9C8 = 6.
Look at cell R1C1.
Every other digit already appears in its row, column or box.
Only one option remains: R1C1 = 8.
Look at cell R1C3.
Every other digit already appears in its row, column or box.
Only one option remains: R1C3 = 6.
Look at cell R1C4.
Every other digit already appears in its row, column or box.
Only one option remains: R1C4 = 4.
Look at cell R3C3.
Every other digit already appears in its row, column or box.
Only one option remains: R3C3 = 1.
Look at cell R4C1.
Every other digit already appears in its row, column or box.
Only one option remains: R4C1 = 3.
Look at cell R4C4.
Every other digit already appears in its row, column or box.
Only one option remains: R4C4 = 8.
Look at cell R4C6.
Every other digit already appears in its row, column or box.
Only one option remains: R4C6 = 4.
Look at cell R5C3.
Every other digit already appears in its row, column or box.
Only one option remains: R5C3 = 8.
Look at cell R5C4.
Every other digit already appears in its row, column or box.
Only one option remains: R5C4 = 3.
Look at cell R7C1.
Every other digit already appears in its row, column or box.
Only one option remains: R7C1 = 4.
Look at cell R7C4.
Every other digit already appears in its row, column or box.
Only one option remains: R7C4 = 6.
Look at cell R7C6.
Every other digit already appears in its row, column or box.
Only one option remains: R7C6 = 1.
Look at cell R7C8.
Every other digit already appears in its row, column or box.
Only one option remains: R7C8 = 3.