Step-by-step solution
Steps 61
Estimated time 100 – 150 min
Hardest technique X-Wing
Clues 23
Given digit (clue)
Solved digit
Placement (✓ RlCc=d)
Elimination (✗ RlCc≠d)
Look at cell R7C5.
Every other digit already appears in its row, column or box.
Only one option remains: R7C5 = 8.
Scan the empty cells in this column where 9 could go.
Across the whole column, 9 has only one possible spot left.
So R1C2 = 9.
Scan the empty cells in this column where 5 could go.
Across the whole column, 5 has only one possible spot left.
So R1C9 = 5.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R2C4 = 5.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R3C3 = 5.
Scan the empty cells in this row where 5 could go.
Across the whole row, 5 has only one possible spot left.
So R4C1 = 5.
Scan the empty cells in this column where 9 could go.
Across the whole column, 9 has only one possible spot left.
So R4C7 = 9.
Scan the empty cells in this row where 9 could go.
Across the whole row, 9 has only one possible spot left.
So R6C4 = 9.
Scan the empty cells in this row where 1 could go.
Across the whole row, 1 has only one possible spot left.
So R7C2 = 1.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R7C6 = 5.
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R8C5 = 9.
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R9C1 = 9.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R9C3 = 8.
Look at cell R8C1.
Every other digit already appears in its row, column or box.
Only one option remains: R8C1 = 7.
Look at cell R8C7.
Every other digit already appears in its row, column or box.
Only one option remains: R8C7 = 6.
Look at cell R7C3.
Every other digit already appears in its row, column or box.
Only one option remains: R7C3 = 3.
Look at cell R7C9.
Every other digit already appears in its row, column or box.
Only one option remains: R7C9 = 2.
Look at cell R8C4.
Every other digit already appears in its row, column or box.
Only one option remains: R8C4 = 4.
Look at cell R9C4.
Every other digit already appears in its row, column or box.
Only one option remains: R9C4 = 2.
Look at cell R9C9.
Every other digit already appears in its row, column or box.
Only one option remains: R9C9 = 4.
Look at cell R4C9.
Every other digit already appears in its row, column or box.
Only one option remains: R4C9 = 1.
Look at cell R6C3.
Every other digit already appears in its row, column or box.
Only one option remains: R6C3 = 7.
Look at cell R6C9.
Every other digit already appears in its row, column or box.
Only one option remains: R6C9 = 6.
Look at cell R7C4.
Every other digit already appears in its row, column or box.
Only one option remains: R7C4 = 6.
Look at cell R7C7.
Every other digit already appears in its row, column or box.
Only one option remains: R7C7 = 7.
Look at cell R9C8.
Every other digit already appears in its row, column or box.
Only one option remains: R9C8 = 3.
Look at cell R1C3.
Every other digit already appears in its row, column or box.
Only one option remains: R1C3 = 4.
Scan the empty cells in this column where 1 could go.
Across the whole column, 1 has only one possible spot left.
So R1C5 = 1.
Scan the empty cells in this column where 7 could go.
Across the whole column, 7 has only one possible spot left.
So R3C2 = 7.
Scan the empty cells in this box where 1 could go.
Across the whole box, 1 has only one possible spot left.
So R3C7 = 1.
Scan the empty cells in this column where 7 could go.
Across the whole column, 7 has only one possible spot left.
So R4C8 = 7.
Scan the empty cells in this box where 1 could go.
Across the whole box, 1 has only one possible spot left.
So R5C4 = 1.
Scan the empty cells in this box where 7 could go.
Across the whole box, 7 has only one possible spot left.
So R5C6 = 7.
Scan the empty cells in this row where 1 could go.
Across the whole row, 1 has only one possible spot left.
So R6C1 = 1.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R6C2 = 3.
Scan the empty cells in this row where 7 could go.
Across the whole row, 7 has only one possible spot left.
So R1C4 = 7.
Scan the empty cells in this row where 4 could go.
Across the whole row, 4 has only one possible spot left.
So R5C2 = 4.
Find 8 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 8.
R3C1 is seen by both free ends: 8 is therefore eliminated there.
Find 2 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 2.
R2C7 is seen by both free ends: 2 is therefore eliminated there.
Find 8 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 8.
R2C7 is seen by both free ends: 8 is therefore eliminated there.
Look at cell R2C7.
Every other digit already appears in its row, column or box.
Only one option remains: R2C7 = 3.
Look at cell R2C5.
Every other digit already appears in its row, column or box.
Only one option remains: R2C5 = 4.
Look at cell R4C5.
Every other digit already appears in its row, column or box.
Only one option remains: R4C5 = 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 R6C6.
Every other digit already appears in its row, column or box.
Only one option remains: R6C6 = 2.
Look at cell R6C8.
Every other digit already appears in its row, column or box.
Only one option remains: R6C8 = 8.
Look at cell R3C4.
Every other digit already appears in its row, column or box.
Only one option remains: R3C4 = 3.
Look at cell R4C2.
Every other digit already appears in its row, column or box.
Only one option remains: R4C2 = 2.
Look at cell R4C6.
Every other digit already appears in its row, column or box.
Only one option remains: R4C6 = 4.
Look at cell R5C1.
Every other digit already appears in its row, column or box.
Only one option remains: R5C1 = 8.
Look at cell R5C7.
Every other digit already appears in its row, column or box.
Only one option remains: R5C7 = 2.
Look at cell R1C7.
Every other digit already appears in its row, column or box.
Only one option remains: R1C7 = 8.
Look at cell R2C2.
Every other digit already appears in its row, column or box.
Only one option remains: R2C2 = 8.
Look at cell R3C1.
Every other digit already appears in its row, column or box.
Only one option remains: R3C1 = 6.
Look at cell R3C6.
Every other digit already appears in its row, column or box.
Only one option remains: R3C6 = 8.
Look at cell R3C8.
Every other digit already appears in its row, column or box.
Only one option remains: R3C8 = 4.
Look at cell R1C6.
Every other digit already appears in its row, column or box.
Only one option remains: R1C6 = 6.
Look at cell R1C8.
Every other digit already appears in its row, column or box.
Only one option remains: R1C8 = 2.
Look at cell R2C1.
Every other digit already appears in its row, column or box.
Only one option remains: R2C1 = 2.
Look at cell R2C8.
Every other digit already appears in its row, column or box.
Only one option remains: R2C8 = 6.
Look at cell R1C1.
Every other digit already appears in its row, column or box.
Only one option remains: R1C1 = 3.