Sudoku Solution No. 63

Hard Score 72 / 100
Digits appear one by one.

Step-by-step solution

Steps 64 Estimated time 104 – 156 min Hardest technique X-Wing Clues 23
Given digit (clue) Solved digit Placement (✓ RlCc=d) Elimination (✗ RlCc≠d)
1 Hidden Single ✓ R2C9=5
Scan the empty cells in this box where 5 could go. Across the whole box, 5 has only one possible spot left. So R2C9 = 5.
2 Hidden Single ✓ R3C3=5
Scan the empty cells in this column where 5 could go. Across the whole column, 5 has only one possible spot left. So R3C3 = 5.
3 Hidden Single ✓ R3C6=8
Scan the empty cells in this row where 8 could go. Across the whole row, 8 has only one possible spot left. So R3C6 = 8.
4 Hidden Single ✓ R4C5=5
Scan the empty cells in this column where 5 could go. Across the whole column, 5 has only one possible spot left. So R4C5 = 5.
5 Hidden Single ✓ R5C2=8
Scan the empty cells in this row where 8 could go. Across the whole row, 8 has only one possible spot left. So R5C2 = 8.
6 Hidden Single ✓ R6C7=5
Scan the empty cells in this box where 5 could go. Across the whole box, 5 has only one possible spot left. So R6C7 = 5.
7 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.
8 Hidden Single ✓ R7C9=3
Scan the empty cells in this row where 3 could go. Across the whole row, 3 has only one possible spot left. So R7C9 = 3.
9 Hidden Single ✓ R8C1=8
Scan the empty cells in this column where 8 could go. Across the whole column, 8 has only one possible spot left. So R8C1 = 8.
10 Hidden Single ✓ R8C2=6
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.
11 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.
12 Hidden Single ✓ R8C6=3
Scan the empty cells in this column where 3 could go. Across the whole column, 3 has only one possible spot left. So R8C6 = 3.
13 Hidden Single ✓ R8C7=9
Scan the empty cells in this box where 9 could go. Across the whole box, 9 has only one possible spot left. So R8C7 = 9.
14 Hidden Single ✓ R9C9=8
Scan the empty cells in this box where 8 could go. Across the whole box, 8 has only one possible spot left. So R9C9 = 8.
15 Hidden Single ✓ R5C3=3
Scan the empty cells in this column where 3 could go. Across the whole column, 3 has only one possible spot left. So R5C3 = 3.
16 Hidden Single ✓ R6C2=2
Scan the empty cells in this box where 2 could go. Across the whole box, 2 has only one possible spot left. So R6C2 = 2.
17 Hidden Single ✓ R6C8=3
Scan the empty cells in this box where 3 could go. Across the whole box, 3 has only one possible spot left. So R6C8 = 3.
18 Naked Single ✓ R7C2=7
Look at cell R7C2. Every other digit already appears in its row, column or box. Only one option remains: R7C2 = 7.
19 Naked Single ✓ R7C5=2
Look at cell R7C5. Every other digit already appears in its row, column or box. Only one option remains: R7C5 = 2.
20 Hidden Single ✓ R6C6=4
Scan the empty cells in this row where 4 could go. Across the whole row, 4 has only one possible spot left. So R6C6 = 4.
21 Hidden Single ✓ R8C8=7
Scan the empty cells in this row where 7 could go. Across the whole row, 7 has only one possible spot left. So R8C8 = 7.
22 Naked Pair ✗ 2 eliminations
Spot R8C3 and R9C3 on this column. These two cells can only hold 1 and 2: they reserve those digits. 1 and 2 are therefore removed from the other cells of the column.
23 Pointing ✗ 2 eliminations
(1) Look at where 4 can go in this box. (2) Look at where 7 can go in this box. (1) All its spots lie on a single row (R4C2 and R4C3). (2) All its spots lie on a single row (R4C1 and R4C3). (1) 4 is therefore removed from that row outside the box. (2) 7 is therefore removed from that row outside the box.
24 Hidden Single ✓ R1C9=4
Scan the empty cells in this column where 4 could go. Across the whole column, 4 has only one possible spot left. So R1C9 = 4.
25 Hidden Single ✓ R2C2=4
Scan the empty cells in this box where 4 could go. Across the whole box, 4 has only one possible spot left. So R2C2 = 4.
26 Hidden Single ✓ R4C1=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R4C1 = 7.
27 Hidden Single ✓ 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 R4C3 = 4.
28 Naked Single ✓ R1C3=7
Look at cell R1C3. Every other digit already appears in its row, column or box. Only one option remains: R1C3 = 7.
29 Hidden Single ✓ R1C7=2
Scan the empty cells in this box where 2 could go. Across the whole box, 2 has only one possible spot left. So R1C7 = 2.
30 Hidden Single ✓ R2C7=3
Scan the empty cells in this row where 3 could go. Across the whole row, 3 has only one possible spot left. So R2C7 = 3.
31 Hidden Single ✓ R3C2=3
Scan the empty cells in this column where 3 could go. Across the whole column, 3 has only one possible spot left. So R3C2 = 3.
32 Hidden Single ✓ R3C7=7
Scan the empty cells in this box where 7 could go. Across the whole box, 7 has only one possible spot left. So R3C7 = 7.
33 Hidden Single ✓ R8C9=2
Scan the empty cells in this column where 2 could go. Across the whole column, 2 has only one possible spot left. So R8C9 = 2.
34 Hidden Single ✓ R9C3=2
Scan the empty cells in this box where 2 could go. Across the whole box, 2 has only one possible spot left. So R9C3 = 2.
35 Naked Single ✓ R8C3=1
Look at cell R8C3. Every other digit already appears in its row, column or box. Only one option remains: R8C3 = 1.
36 Skyscraper ✗ 2 eliminations
Find 6 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 6. R2C6 and R5C5 is seen by both free ends: 6 is therefore eliminated there.
37 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. R1C4 is seen by both free ends: 1 is therefore eliminated there.
38 Box/Line ✗ 1 elimination
Look at where 1 can go on this row. All its spots lie within a single box (R1C1 and R1C2). 1 is therefore removed from the rest of the box.
39 Two-String Kite ✗ 1 elimination
Find 9 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 9. R1C4 is seen by both free ends: 9 is therefore eliminated there.
40 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.
41 Naked Single ✓ R3C5=1
Look at cell R3C5. Every other digit already appears in its row, column or box. Only one option remains: R3C5 = 1.
42 Naked Single ✓ R3C9=6
Look at cell R3C9. Every other digit already appears in its row, column or box. Only one option remains: R3C9 = 6.
43 Naked Single ✓ R4C9=1
Look at cell R4C9. Every other digit already appears in its row, column or box. Only one option remains: R4C9 = 1.
44 Naked Single ✓ R5C5=7
Look at cell R5C5. Every other digit already appears in its row, column or box. Only one option remains: R5C5 = 7.
45 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.
46 Naked Single ✓ R5C8=6
Look at cell R5C8. Every other digit already appears in its row, column or box. Only one option remains: R5C8 = 6.
47 Naked Single ✓ R9C7=1
Look at cell R9C7. Every other digit already appears in its row, column or box. Only one option remains: R9C7 = 1.
48 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.
49 Naked Single ✓ R2C5=9
Look at cell R2C5. Every other digit already appears in its row, column or box. Only one option remains: R2C5 = 9.
50 Naked Single ✓ R2C8=1
Look at cell R2C8. Every other digit already appears in its row, column or box. Only one option remains: R2C8 = 1.
51 Naked Single ✓ R4C2=9
Look at cell R4C2. Every other digit already appears in its row, column or box. Only one option remains: R4C2 = 9.
52 Naked Single ✓ R4C6=6
Look at cell R4C6. Every other digit already appears in its row, column or box. Only one option remains: R4C6 = 6.
53 Naked Single ✓ R5C6=2
Look at cell R5C6. Every other digit already appears in its row, column or box. Only one option remains: R5C6 = 2.
54 Naked Single ✓ R6C1=1
Look at cell R6C1. Every other digit already appears in its row, column or box. Only one option remains: R6C1 = 1.
55 Naked Single ✓ R6C4=9
Look at cell R6C4. Every other digit already appears in its row, column or box. Only one option remains: R6C4 = 9.
56 Naked Single ✓ R9C4=7
Look at cell R9C4. Every other digit already appears in its row, column or box. Only one option remains: R9C4 = 7.
57 Naked Single ✓ R9C5=6
Look at cell R9C5. Every other digit already appears in its row, column or box. Only one option remains: R9C5 = 6.
58 Naked Single ✓ R9C6=9
Look at cell R9C6. Every other digit already appears in its row, column or box. Only one option remains: R9C6 = 9.
59 Naked Single ✓ R1C1=9
Look at cell R1C1. Every other digit already appears in its row, column or box. Only one option remains: R1C1 = 9.
60 Naked Single ✓ R1C2=1
Look at cell R1C2. Every other digit already appears in its row, column or box. Only one option remains: R1C2 = 1.
61 Naked Single ✓ R2C1=6
Look at cell R2C1. Every other digit already appears in its row, column or box. Only one option remains: R2C1 = 6.
62 Naked Single ✓ R2C4=2
Look at cell R2C4. Every other digit already appears in its row, column or box. Only one option remains: R2C4 = 2.
63 Naked Single ✓ R2C6=7
Look at cell R2C6. Every other digit already appears in its row, column or box. Only one option remains: R2C6 = 7.
64 Naked Single ✓ R5C4=1
Look at cell R5C4. Every other digit already appears in its row, column or box. Only one option remains: R5C4 = 1.