Step-by-step solution
Steps 67
Estimated time 68 – 102 min
Hardest technique Box/Line
Clues 22
Given digit (clue)
Solved digit
Placement (✓ RlCc=d)
Elimination (✗ RlCc≠d)
Look at cell R1C3.
Every other digit already appears in its row, column or box.
Only one option remains: R1C3 = 6.
Look at cell R1C1.
Every other digit already appears in its row, column or box.
Only one option remains: R1C1 = 3.
Look at cell R1C2.
Every other digit already appears in its row, column or box.
Only one option remains: R1C2 = 1.
Look at cell R2C2.
Every other digit already appears in its row, column or box.
Only one option remains: R2C2 = 8.
Scan the empty cells in this box where 2 could go.
Across the whole box, 2 has only one possible spot left.
So R1C8 = 2.
Scan the empty cells in this row where 6 could go.
Across the whole row, 6 has only one possible spot left.
So R2C8 = 6.
Scan the empty cells in this box where 4 could go.
Across the whole box, 4 has only one possible spot left.
So R3C1 = 4.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R3C2 = 5.
Scan the empty cells in this row where 3 could go.
Across the whole row, 3 has only one possible spot left.
So R3C5 = 3.
Scan the empty cells in this box where 8 could go.
Across the whole box, 8 has only one possible spot left.
So R3C6 = 8.
Scan the empty cells in this column where 4 could go.
Across the whole column, 4 has only one possible spot left.
So R4C3 = 4.
Scan the empty cells in this box where 4 could go.
Across the whole box, 4 has only one possible spot left.
So R5C6 = 4.
Scan the empty cells in this column where 7 could go.
Across the whole column, 7 has only one possible spot left.
So R6C2 = 7.
Scan the empty cells in this column where 3 could go.
Across the whole column, 3 has only one possible spot left.
So R6C4 = 3.
Scan the empty cells in this box where 4 could go.
Across the whole box, 4 has only one possible spot left.
So R6C7 = 4.
Scan the empty cells in this row where 4 could go.
Across the whole row, 4 has only one possible spot left.
So R7C2 = 4.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R7C7 = 6.
Scan the empty cells in this column where 6 could go.
Across the whole column, 6 has only one possible spot left.
So R9C1 = 6.
Spot R8C3 and R9C3 in this box.
These two cells can only hold 5 and 8: they reserve those digits.
5 and 8 are therefore removed from the other cells of the box.
Find where 3 and 7 can go in this box.
These two digits only fit in R8C9 and R9C8 in the box.
The other candidates in R8C9 and R9C8 are therefore eliminated.
Scan the empty cells in this box where 5 could go.
Across the whole box, 5 has only one possible spot left.
So R8C3 = 5.
Scan the empty cells in this row where 8 could go.
Across the whole row, 8 has only one possible spot left.
So R9C3 = 8.
Scan the empty cells in this box where 1 could go.
Across the whole box, 1 has only one possible spot left.
So R8C4 = 1.
Scan the empty cells in this row where 8 could go.
Across the whole row, 8 has only one possible spot left.
So R8C5 = 8.
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 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 9 could go.
Across the whole box, 9 has only one possible spot left.
So R3C9 = 9.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R4C9 = 3.
Scan the empty cells in this row where 7 could go.
Across the whole row, 7 has only one possible spot left.
So R8C9 = 7.
Scan the empty cells in this column where 7 could go.
Across the whole column, 7 has only one possible spot left.
So R9C4 = 7.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R9C8 = 3.
Scan the empty cells in this row where 3 could go.
Across the whole row, 3 has only one possible spot left.
So R8C2 = 3.
Spot R5C2 and R5C4 on this row.
These two cells can only hold 2 and 9: they reserve those digits.
2 and 9 are therefore removed from the other cells of the row.
Find 2 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 2.
R9C6 is seen by both free ends: 2 is therefore eliminated there.
Look at where 2 can go in this box.
All its spots lie on a single row (R7C4 and R7C5).
2 is therefore removed from that row outside the box.
Look at cell R7C9.
Every other digit already appears in its row, column or box.
Only one option remains: R7C9 = 8.
Look at cell R5C9.
Every other digit already appears in its row, column or box.
Only one option remains: R5C9 = 6.
Look at cell R6C9.
Every other digit already appears in its row, column or box.
Only one option remains: R6C9 = 2.
Scan the empty cells in this row where 6 could go.
Across the whole row, 6 has only one possible spot left.
So R6C5 = 6.
Spot R6C6 and R9C6 on this column.
These two cells can only hold 5 and 9: they reserve those digits.
5 and 9 are therefore removed from the other cells of the column.
Look at cell R1C6.
Every other digit already appears in its row, column or box.
Only one option remains: R1C6 = 7.
Look at cell R1C5.
Every other digit already appears in its row, column or box.
Only one option remains: R1C5 = 9.
Scan the empty cells in this row where 7 could go.
Across the whole row, 7 has only one possible spot left.
So R4C5 = 7.
Find 5 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 5.
R6C8 is seen by both free ends: 5 is therefore eliminated there.
Find 9 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 9.
R9C6 is seen by both free ends: 9 is therefore eliminated there.
Look at cell R9C6.
Every other digit already appears in its row, column or box.
Only one option remains: R9C6 = 5.
Look at cell R6C6.
Every other digit already appears in its row, column or box.
Only one option remains: R6C6 = 9.
Look at cell R6C8.
Every other digit already appears in its row, column or box.
Only one option remains: R6C8 = 8.
Look at cell R7C5.
Every other digit already appears in its row, column or box.
Only one option remains: R7C5 = 2.
Look at cell R2C5.
Every other digit already appears in its row, column or box.
Only one option remains: R2C5 = 1.
Look at cell R2C6.
Every other digit already appears in its row, column or box.
Only one option remains: R2C6 = 2.
Look at cell R4C6.
Every other digit already appears in its row, column or box.
Only one option remains: R4C6 = 1.
Look at cell R5C4.
Every other digit already appears in its row, column or box.
Only one option remains: R5C4 = 2.
Look at cell R5C5.
Every other digit already appears in its row, column or box.
Only one option remains: R5C5 = 5.
Look at cell R5C8.
Every other digit already appears in its row, column or box.
Only one option remains: R5C8 = 1.
Look at cell R6C1.
Every other digit already appears in its row, column or box.
Only one option remains: R6C1 = 5.
Look at cell R7C4.
Every other digit already appears in its row, column or box.
Only one option remains: R7C4 = 9.
Look at cell R7C8.
Every other digit already appears in its row, column or box.
Only one option remains: R7C8 = 5.
Look at cell R4C8.
Every other digit already appears in its row, column or box.
Only one option remains: R4C8 = 9.
Look at cell R5C1.
Every other digit already appears in its row, column or box.
Only one option remains: R5C1 = 8.
Look at cell R5C2.
Every other digit already appears in its row, column or box.
Only one option remains: R5C2 = 9.
Look at cell R9C2.
Every other digit already appears in its row, column or box.
Only one option remains: R9C2 = 2.
Look at cell R9C7.
Every other digit already appears in its row, column or box.
Only one option remains: R9C7 = 9.
Look at cell R4C1.
Every other digit already appears in its row, column or box.
Only one option remains: R4C1 = 2.
Look at cell R4C7.
Every other digit already appears in its row, column or box.
Only one option remains: R4C7 = 5.
Look at cell R8C1.
Every other digit already appears in its row, column or box.
Only one option remains: R8C1 = 9.
Look at cell R8C7.
Every other digit already appears in its row, column or box.
Only one option remains: R8C7 = 2.