Sudoku Solution No. 146

Hard Score 73 / 100
Digits appear one by one.

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)
1 Hidden Single ✓ R1C2=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R1C2 = 7.
2 Hidden Single ✓ R1C6=5
Scan the empty cells in this box where 5 could go. Across the whole box, 5 has only one possible spot left. So R1C6 = 5.
3 Hidden Single ✓ R2C3=2
Scan the empty cells in this box where 2 could go. Across the whole box, 2 has only one possible spot left. So R2C3 = 2.
4 Hidden Single ✓ R2C5=6
Scan the empty cells in this row where 6 could go. Across the whole row, 6 has only one possible spot left. So R2C5 = 6.
5 Hidden Single ✓ R3C1=5
Scan the empty cells in this box where 5 could go. Across the whole box, 5 has only one possible spot left. So R3C1 = 5.
6 Hidden Single ✓ R3C6=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R3C6 = 7.
7 Hidden Single ✓ R3C8=3
Scan the empty cells in this box where 3 could go. Across the whole box, 3 has only one possible spot left. So R3C8 = 3.
8 Hidden Single ✓ R4C4=7
Scan the empty cells in this row where 7 could go. Across the whole row, 7 has only one possible spot left. So R4C4 = 7.
9 Hidden Single ✓ R5C1=2
Scan the empty cells in this column where 2 could go. Across the whole column, 2 has only one possible spot left. So R5C1 = 2.
10 Hidden Single ✓ R6C6=8
Scan the empty cells in this box where 8 could go. Across the whole box, 8 has only one possible spot left. So R6C6 = 8.
11 Hidden Single ✓ R7C4=8
Scan the empty cells in this box where 8 could go. Across the whole box, 8 has only one possible spot left. So R7C4 = 8.
12 Hidden Single ✓ R7C5=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R7C5 = 7.
13 Hidden Single ✓ R7C8=6
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.
14 Hidden Single ✓ R8C2=8
Scan the empty cells in this column where 8 could go. Across the whole column, 8 has only one possible spot left. So R8C2 = 8.
15 Hidden Single ✓ R8C4=5
Scan the empty cells in this row where 5 could go. Across the whole row, 5 has only one possible spot left. So R8C4 = 5.
16 Hidden Single ✓ 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 R8C9 = 7.
17 Hidden Single ✓ R9C3=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R9C3 = 7.
18 Hidden Single ✓ R9C5=2
Scan the empty cells in this row where 2 could go. Across the whole row, 2 has only one possible spot left. So R9C5 = 2.
19 Naked Single ✓ R2C9=1
Look at cell R2C9. Every other digit already appears in its row, column or box. Only one option remains: R2C9 = 1.
20 Naked Single ✓ R3C9=8
Look at cell R3C9. Every other digit already appears in its row, column or box. Only one option remains: R3C9 = 8.
21 Naked Single ✓ R2C2=9
Look at cell R2C2. Every other digit already appears in its row, column or box. Only one option remains: R2C2 = 9.
22 Naked Single ✓ R2C6=3
Look at cell R2C6. Every other digit already appears in its row, column or box. Only one option remains: R2C6 = 3.
23 Naked Single ✓ R3C2=1
Look at cell R3C2. Every other digit already appears in its row, column or box. Only one option remains: R3C2 = 1.
24 Naked Single ✓ R3C5=9
Look at cell R3C5. Every other digit already appears in its row, column or box. Only one option remains: R3C5 = 9.
25 Naked Single ✓ R1C4=1
Look at cell R1C4. Every other digit already appears in its row, column or box. Only one option remains: R1C4 = 1.
26 Naked Single ✓ R1C5=8
Look at cell R1C5. Every other digit already appears in its row, column or box. Only one option remains: R1C5 = 8.
27 Naked Single ✓ R9C4=3
Look at cell R9C4. Every other digit already appears in its row, column or box. Only one option remains: R9C4 = 3.
28 Hidden Single ✓ R4C8=8
Scan the empty cells in this row where 8 could go. Across the whole row, 8 has only one possible spot left. So R4C8 = 8.
29 Hidden Single ✓ R8C1=9
Scan the empty cells in this box where 9 could go. Across the whole box, 9 has only one possible spot left. So R8C1 = 9.
30 Hidden Single ✓ R8C3=3
Scan the empty cells in this row where 3 could go. Across the whole row, 3 has only one possible spot left. So R8C3 = 3.
31 Naked Pair ✗ 1 elimination
Spot R4C3 and R6C3 in this box. These two cells can only hold 1 and 9: they reserve those digits. 1 and 9 are therefore removed from the other cells of the box.
32 Naked Pair ✗ 3 eliminations
Spot R4C1 and R4C9 on this row. These two cells can only hold 4 and 6: they reserve those digits. 4 and 6 are therefore removed from the other cells of the row.
33 Naked Single ✓ R4C2=3
Look at cell R4C2. Every other digit already appears in its row, column or box. Only one option remains: R4C2 = 3.
34 Hidden Single ✓ R5C5=3
Scan the empty cells in this row where 3 could go. Across the whole row, 3 has only one possible spot left. So R5C5 = 3.
35 Hidden Single ✓ R6C7=3
Scan the empty cells in this column where 3 could go. Across the whole column, 3 has only one possible spot left. So R6C7 = 3.
36 Two-String Kite ✗ 1 elimination
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. R8C8 is seen by both free ends: 1 is therefore eliminated there.
37 Pointing ✗ 1 elimination
Look at where 1 can go in this box. All its spots lie on a single column (R7C7 and R8C7). 1 is therefore removed from that column outside the box.
38 Naked Single ✓ R4C7=9
Look at cell R4C7. Every other digit already appears in its row, column or box. Only one option remains: R4C7 = 9.
39 Naked Single ✓ R4C3=1
Look at cell R4C3. Every other digit already appears in its row, column or box. Only one option remains: R4C3 = 1.
40 Naked Single ✓ R6C3=9
Look at cell R6C3. Every other digit already appears in its row, column or box. Only one option remains: R6C3 = 9.
41 Naked Single ✓ R6C4=6
Look at cell R6C4. Every other digit already appears in its row, column or box. Only one option remains: R6C4 = 6.
42 Naked Single ✓ R5C4=9
Look at cell R5C4. Every other digit already appears in its row, column or box. Only one option remains: R5C4 = 9.
43 Hidden Single ✓ R1C8=9
Scan the empty cells in this row where 9 could go. Across the whole row, 9 has only one possible spot left. So R1C8 = 9.
44 Naked Pair ✗ 2 eliminations
Spot R5C6 and R5C8 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.
45 Skyscraper ✗ 1 elimination
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. R9C6 is seen by both free ends: 4 is therefore eliminated there.
46 Naked Single ✓ R9C6=1
Look at cell R9C6. Every other digit already appears in its row, column or box. Only one option remains: R9C6 = 1.
47 Naked Single ✓ R5C6=4
Look at cell R5C6. Every other digit already appears in its row, column or box. Only one option remains: R5C6 = 4.
48 Naked Single ✓ R5C8=1
Look at cell R5C8. Every other digit already appears in its row, column or box. Only one option remains: R5C8 = 1.
49 Naked Single ✓ R6C5=1
Look at cell R6C5. Every other digit already appears in its row, column or box. Only one option remains: R6C5 = 1.
50 Naked Single ✓ R8C5=4
Look at cell R8C5. Every other digit already appears in its row, column or box. Only one option remains: R8C5 = 4.
51 Naked Single ✓ R8C8=2
Look at cell R8C8. Every other digit already appears in its row, column or box. Only one option remains: R8C8 = 2.
52 Naked Single ✓ R6C8=4
Look at cell R6C8. Every other digit already appears in its row, column or box. Only one option remains: R6C8 = 4.
53 Naked Single ✓ R8C7=1
Look at cell R8C7. Every other digit already appears in its row, column or box. Only one option remains: R8C7 = 1.
54 Naked Single ✓ R4C9=6
Look at cell R4C9. Every other digit already appears in its row, column or box. Only one option remains: R4C9 = 6.
55 Naked Single ✓ R5C9=5
Look at cell R5C9. Every other digit already appears in its row, column or box. Only one option remains: R5C9 = 5.
56 Naked Single ✓ R6C2=5
Look at cell R6C2. Every other digit already appears in its row, column or box. Only one option remains: R6C2 = 5.
57 Naked Single ✓ R6C9=2
Look at cell R6C9. Every other digit already appears in its row, column or box. Only one option remains: R6C9 = 2.
58 Naked Single ✓ R7C7=4
Look at cell R7C7. Every other digit already appears in its row, column or box. Only one option remains: R7C7 = 4.
59 Naked Single ✓ R1C7=2
Look at cell R1C7. Every other digit already appears in its row, column or box. Only one option remains: R1C7 = 2.
60 Naked Single ✓ R1C9=4
Look at cell R1C9. Every other digit already appears in its row, column or box. Only one option remains: R1C9 = 4.
61 Naked Single ✓ R4C1=4
Look at cell R4C1. Every other digit already appears in its row, column or box. Only one option remains: R4C1 = 4.
62 Naked Single ✓ R5C2=6
Look at cell R5C2. Every other digit already appears in its row, column or box. Only one option remains: R5C2 = 6.
63 Naked Single ✓ R7C1=1
Look at cell R7C1. Every other digit already appears in its row, column or box. Only one option remains: R7C1 = 1.
64 Naked Single ✓ R9C1=6
Look at cell R9C1. Every other digit already appears in its row, column or box. Only one option remains: R9C1 = 6.
65 Naked Single ✓ R9C2=4
Look at cell R9C2. Every other digit already appears in its row, column or box. Only one option remains: R9C2 = 4.