Sudoku Solution No. 148

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 ✓ R1C7=8
Scan the empty cells in this box where 8 could go. Across the whole box, 8 has only one possible spot left. So R1C7 = 8.
2 Hidden Single ✓ R2C2=8
Scan the empty cells in this box where 8 could go. Across the whole box, 8 has only one possible spot left. So R2C2 = 8.
3 Hidden Single ✓ R4C3=1
Scan the empty cells in this box where 1 could go. Across the whole box, 1 has only one possible spot left. So R4C3 = 1.
4 Hidden Single ✓ R5C3=9
Scan the empty cells in this row where 9 could go. Across the whole row, 9 has only one possible spot left. So R5C3 = 9.
5 Hidden Single ✓ R5C4=1
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.
6 Hidden Single ✓ R5C9=8
Scan the empty cells in this box where 8 could go. Across the whole box, 8 has only one possible spot left. So R5C9 = 8.
7 Hidden Single ✓ R8C6=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R8C6 = 7.
8 Hidden Single ✓ R9C2=7
Scan the empty cells in this column where 7 could go. Across the whole column, 7 has only one possible spot left. So R9C2 = 7.
9 Hidden Single ✓ R9C3=8
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.
10 Hidden Single ✓ R1C1=1
Scan the empty cells in this row where 1 could go. Across the whole row, 1 has only one possible spot left. So R1C1 = 1.
11 Hidden Single ✓ R4C4=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R4C4 = 7.
12 Hidden Single ✓ R6C7=7
Scan the empty cells in this column where 7 could go. Across the whole column, 7 has only one possible spot left. So R6C7 = 7.
13 Hidden Single ✓ R4C5=2
Scan the empty cells in this box where 2 could go. Across the whole box, 2 has only one possible spot left. So R4C5 = 2.
14 Hidden Single ✓ R6C4=3
Scan the empty cells in this box where 3 could go. Across the whole box, 3 has only one possible spot left. So R6C4 = 3.
15 Hidden Single ✓ R9C4=2
Scan the empty cells in this column where 2 could go. Across the whole column, 2 has only one possible spot left. So R9C4 = 2.
16 Naked Single ✓ R4C6=4
Look at cell R4C6. Every other digit already appears in its row, column or box. Only one option remains: R4C6 = 4.
17 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.
18 Naked Single ✓ R7C5=1
Look at cell R7C5. Every other digit already appears in its row, column or box. Only one option remains: R7C5 = 1.
19 Hidden Single ✓ R1C8=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R1C8 = 7.
20 Hidden Single ✓ R2C6=9
Scan the empty cells in this box where 9 could go. Across the whole box, 9 has only one possible spot left. So R2C6 = 9.
21 Hidden Single ✓ R2C7=6
Scan the empty cells in this box where 6 could go. Across the whole box, 6 has only one possible spot left. So R2C7 = 6.
22 Hidden Single ✓ R2C9=2
Scan the empty cells in this box where 2 could go. Across the whole box, 2 has only one possible spot left. So R2C9 = 2.
23 Hidden Single ✓ R3C3=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R3C3 = 7.
24 Hidden Single ✓ R3C5=8
Scan the empty cells in this box where 8 could go. Across the whole box, 8 has only one possible spot left. So R3C5 = 8.
25 Hidden Single ✓ R3C6=1
Scan the empty cells in this row where 1 could go. Across the whole row, 1 has only one possible spot left. So R3C6 = 1.
26 Hidden Single ✓ R3C8=9
Scan the empty cells in this box where 9 could go. Across the whole box, 9 has only one possible spot left. So R3C8 = 9.
27 Hidden Single ✓ R6C5=9
Scan the empty cells in this box where 9 could go. Across the whole box, 9 has only one possible spot left. So R6C5 = 9.
28 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.
29 Hidden Single ✓ R7C1=9
Scan the empty cells in this box where 9 could go. Across the whole box, 9 has only one possible spot left. So R7C1 = 9.
30 Hidden Single ✓ R8C1=2
Scan the empty cells in this box where 2 could go. Across the whole box, 2 has only one possible spot left. So R8C1 = 2.
31 Hidden Single ✓ R9C7=1
Scan the empty cells in this row where 1 could go. Across the whole row, 1 has only one possible spot left. So R9C7 = 1.
32 Hidden Single ✓ R9C9=9
Scan the empty cells in this box where 9 could go. Across the whole box, 9 has only one possible spot left. So R9C9 = 9.
33 Naked Single ✓ R8C7=3
Look at cell R8C7. Every other digit already appears in its row, column or box. Only one option remains: R8C7 = 3.
34 Naked Pair ✗ 3 eliminations
Spot R1C3 and R8C3 on this column. These two cells can only hold 5 and 6: they reserve those digits. 5 and 6 are therefore removed from the other cells of the column.
35 Pointing ✗ 1 elimination
Look at where 3 can go in this box. All its spots lie on a single column (R4C2 and R5C2). 3 is therefore removed from that column outside the box.
36 Two-String Kite ✗ 1 elimination
Find 6 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 6. R4C2 is seen by both free ends: 6 is therefore eliminated there.
37 Pointing ✗ 1 elimination
Look at where 6 can go in this box. All its spots lie on a single row (R6C1 and R6C2). 6 is therefore removed from that row outside the box.
38 Naked Pair ✗ 4 eliminations
Spot R6C8 and R9C8 on this column. These two cells can only hold 4 and 5: they reserve those digits. 4 and 5 are therefore removed from the other cells of the column.
39 Skyscraper ✗ 1 elimination
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. R7C2 is seen by both free ends: 5 is therefore eliminated there.
40 Hidden Single ✓ R7C3=3
Scan the empty cells in this box where 3 could go. Across the whole box, 3 has only one possible spot left. So R7C3 = 3.
41 Hidden Single ✓ R7C6=5
Scan the empty cells in this row where 5 could go. Across the whole row, 5 has only one possible spot left. So R7C6 = 5.
42 Hidden Single ✓ R9C6=3
Scan the empty cells in this box where 3 could go. Across the whole box, 3 has only one possible spot left. So R9C6 = 3.
43 Naked Single ✓ R2C3=4
Look at cell R2C3. Every other digit already appears in its row, column or box. Only one option remains: R2C3 = 4.
44 Naked Single ✓ R2C4=5
Look at cell R2C4. Every other digit already appears in its row, column or box. Only one option remains: R2C4 = 5.
45 Naked Single ✓ R3C1=6
Look at cell R3C1. Every other digit already appears in its row, column or box. Only one option remains: R3C1 = 6.
46 Naked Single ✓ R3C4=4
Look at cell R3C4. Every other digit already appears in its row, column or box. Only one option remains: R3C4 = 4.
47 Naked Single ✓ R1C3=5
Look at cell R1C3. Every other digit already appears in its row, column or box. Only one option remains: R1C3 = 5.
48 Naked Single ✓ R1C4=6
Look at cell R1C4. Every other digit already appears in its row, column or box. Only one option remains: R1C4 = 6.
49 Naked Single ✓ R2C1=3
Look at cell R2C1. Every other digit already appears in its row, column or box. Only one option remains: R2C1 = 3.
50 Naked Single ✓ R8C3=6
Look at cell R8C3. Every other digit already appears in its row, column or box. Only one option remains: R8C3 = 6.
51 Naked Single ✓ R8C9=5
Look at cell R8C9. Every other digit already appears in its row, column or box. Only one option remains: R8C9 = 5.
52 Naked Single ✓ R9C8=4
Look at cell R9C8. Every other digit already appears in its row, column or box. Only one option remains: R9C8 = 4.
53 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.
54 Naked Single ✓ R6C8=5
Look at cell R6C8. Every other digit already appears in its row, column or box. Only one option remains: R6C8 = 5.
55 Naked Single ✓ R7C2=4
Look at cell R7C2. Every other digit already appears in its row, column or box. Only one option remains: R7C2 = 4.
56 Naked Single ✓ R7C7=2
Look at cell R7C7. Every other digit already appears in its row, column or box. Only one option remains: R7C7 = 2.
57 Naked Single ✓ R7C8=6
Look at cell R7C8. Every other digit already appears in its row, column or box. Only one option remains: R7C8 = 6.
58 Naked Single ✓ R9C1=5
Look at cell R9C1. Every other digit already appears in its row, column or box. Only one option remains: R9C1 = 5.
59 Naked Single ✓ R4C8=3
Look at cell R4C8. Every other digit already appears in its row, column or box. Only one option remains: R4C8 = 3.
60 Naked Single ✓ R5C2=3
Look at cell R5C2. Every other digit already appears in its row, column or box. Only one option remains: R5C2 = 3.
61 Naked Single ✓ R5C7=4
Look at cell R5C7. Every other digit already appears in its row, column or box. Only one option remains: R5C7 = 4.
62 Naked Single ✓ R5C8=2
Look at cell R5C8. Every other digit already appears in its row, column or box. Only one option remains: R5C8 = 2.
63 Naked Single ✓ R6C1=4
Look at cell R6C1. Every other digit already appears in its row, column or box. Only one option remains: R6C1 = 4.
64 Naked Single ✓ R6C2=6
Look at cell R6C2. Every other digit already appears in its row, column or box. Only one option remains: R6C2 = 6.
65 Naked Single ✓ R4C2=5
Look at cell R4C2. Every other digit already appears in its row, column or box. Only one option remains: R4C2 = 5.