Step-by-step solution
Steps 66
Estimated time 68 – 102 min
Hardest technique Box/Line
Clues 22
Given digit (clue)
Solved digit
Placement (✓ RlCc=d)
Elimination (✗ RlCc≠d)
Scan the empty cells in this column where 8 could go.
Across the whole column, 8 has only one possible spot left.
So R1C1 = 8.
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R1C2 = 9.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R1C5 = 6.
Scan the empty cells in this row where 7 could go.
Across the whole row, 7 has only one possible spot left.
So R4C2 = 7.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R4C4 = 3.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R4C6 = 6.
Scan the empty cells in this box where 3 could go.
Across the whole box, 3 has only one possible spot left.
So R5C2 = 3.
Scan the empty cells in this column where 5 could go.
Across the whole column, 5 has only one possible spot left.
So R5C5 = 5.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R5C7 = 6.
Scan the empty cells in this row where 8 could go.
Across the whole row, 8 has only one possible spot left.
So R6C4 = 8.
Scan the empty cells in this box where 9 could go.
Across the whole box, 9 has only one possible spot left.
So R6C6 = 9.
Scan the empty cells in this row where 4 could go.
Across the whole row, 4 has only one possible spot left.
So R6C7 = 4.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R7C8 = 6.
Look at cell R5C4.
Every other digit already appears in its row, column or box.
Only one option remains: R5C4 = 2.
Look at cell R5C9.
Every other digit already appears in its row, column or box.
Only one option remains: R5C9 = 1.
Look at cell R4C8.
Every other digit already appears in its row, column or box.
Only one option remains: R4C8 = 2.
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 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 column where 6 could go.
Across the whole column, 6 has only one possible spot left.
So R6C1 = 6.
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 8 could go.
Across the whole box, 8 has only one possible spot left.
So R8C5 = 8.
Scan the empty cells in this box where 7 could go.
Across the whole box, 7 has only one possible spot left.
So R9C5 = 7.
Look at cell R3C1.
Every other digit already appears in its row, column or box.
Only one option remains: R3C1 = 5.
Look at cell R7C1.
Every other digit already appears in its row, column or box.
Only one option remains: R7C1 = 9.
Look at cell R9C1.
Every other digit already appears in its row, column or box.
Only one option remains: R9C1 = 2.
Scan the empty cells in this column where 5 could go.
Across the whole column, 5 has only one possible spot left.
So R6C2 = 5.
Scan the empty cells in this box where 2 could go.
Across the whole box, 2 has only one possible spot left.
So R6C3 = 2.
Scan the empty cells in this row where 5 could go.
Across the whole row, 5 has only one possible spot left.
So R7C3 = 5.
Scan the empty cells in this column where 9 could go.
Across the whole column, 9 has only one possible spot left.
So R8C4 = 9.
Scan the empty cells in this row where 2 could go.
Across the whole row, 2 has only one possible spot left.
So R8C9 = 2.
Scan the empty cells in this row where 2 could go.
Across the whole row, 2 has only one possible spot left.
So R1C6 = 2.
Scan the empty cells in this column where 2 could go.
Across the whole column, 2 has only one possible spot left.
So R2C2 = 2.
Scan the empty cells in this box where 6 could go.
Across the whole box, 6 has only one possible spot left.
So R2C3 = 6.
Scan the empty cells in this box where 7 could go.
Across the whole box, 7 has only one possible spot left.
So R2C8 = 7.
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.
Spot R9C2 and R9C8 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.
Look at cell R9C3.
Every other digit already appears in its row, column or box.
Only one option remains: R9C3 = 3.
(1) Find where 3 and 5 can go on this row. (2) Find where 3 and 5 can go in this box.
(1) These two digits only fit in R1C7 and R1C9 on the row. (2) These two digits only fit in R1C7 and R1C9 in the box.
(1) The other candidates in R1C7 and R1C9 are therefore eliminated. (2) The other candidates in R1C7 and R1C9 are therefore eliminated.
Look at where 1 can go on this row.
All its spots lie within a single box (R7C4 and R7C6).
1 is therefore removed from the rest of the box.
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.
R1C3 is seen by both free ends: 1 is therefore eliminated there.
Look at where 1 can go in this box.
All its spots lie on a single row (R3C2 and R3C3).
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.
R1C3 is seen by both free ends: 4 is therefore eliminated there.
Look at cell R1C3.
Every other digit already appears in its row, column or box.
Only one option remains: R1C3 = 7.
Scan the empty cells in this row where 7 could go.
Across the whole row, 7 has only one possible spot left.
So R3C4 = 7.
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.
R7C9 is seen by both free ends: 4 is therefore eliminated there.
Look at cell R7C9.
Every other digit already appears in its row, column or box.
Only one option remains: R7C9 = 3.
Look at cell R8C7.
Every other digit already appears in its row, column or box.
Only one option remains: R8C7 = 1.
Look at cell R9C8.
Every other digit already appears in its row, column or box.
Only one option remains: R9C8 = 4.
Look at cell R1C8.
Every other digit already appears in its row, column or box.
Only one option remains: R1C8 = 1.
Look at cell R1C9.
Every other digit already appears in its row, column or box.
Only one option remains: R1C9 = 5.
Look at cell R2C7.
Every other digit already appears in its row, column or box.
Only one option remains: R2C7 = 8.
Look at cell R2C9.
Every other digit already appears in its row, column or box.
Only one option remains: R2C9 = 4.
Look at cell R4C9.
Every other digit already appears in its row, column or box.
Only one option remains: R4C9 = 9.
Look at cell R8C3.
Every other digit already appears in its row, column or box.
Only one option remains: R8C3 = 4.
Look at cell R8C6.
Every other digit already appears in its row, column or box.
Only one option remains: R8C6 = 3.
Look at cell R9C2.
Every other digit already appears in its row, column or box.
Only one option remains: R9C2 = 1.
Look at cell R9C7.
Every other digit already appears in its row, column or box.
Only one option remains: R9C7 = 9.
Look at cell R9C9.
Every other digit already appears in its row, column or box.
Only one option remains: R9C9 = 8.
Look at cell R1C4.
Every other digit already appears in its row, column or box.
Only one option remains: R1C4 = 4.
Look at cell R1C7.
Every other digit already appears in its row, column or box.
Only one option remains: R1C7 = 3.
Look at cell R2C6.
Every other digit already appears in its row, column or box.
Only one option remains: R2C6 = 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 R3C3.
Every other digit already appears in its row, column or box.
Only one option remains: R3C3 = 1.
Look at cell R4C7.
Every other digit already appears in its row, column or box.
Only one option remains: R4C7 = 5.
Look at cell R7C4.
Every other digit already appears in its row, column or box.
Only one option remains: R7C4 = 1.
Look at cell R7C6.
Every other digit already appears in its row, column or box.
Only one option remains: R7C6 = 4.