| Easy Puzzle #20 - One Possible Solution Approach | |||||||||||
| NB: There is only one final solution to this Sudoku puzzle | |||||||||||
| Rules: Place a number from 1-9 in each empty cell so that each row, each column AND each 3x3 block contains all the numbers from 1-9. | |||||||||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | |||||||||||
| 2 | AA | BB | CC | Reference to 3x3 Blocks AA, BB & CC | |||||||
| 3 | |||||||||||
| 4 | |||||||||||
| 5 | DD | EE | FF | Reference to 3x3 Blocks DD, EE & FF | |||||||
| 6 | |||||||||||
| 7 | |||||||||||
| 8 | GG | HH | II | Reference to 3x3 Blocks GG, HH & II | |||||||
| 9 | |||||||||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 1 | 3 | 2 | 6 | Easy Puzzle #20 - October 20, 2005 | ||||||
| 2 | 2 | 7 | 4 | 8 | Original puzzle as published on joe-ks.com | ||||||
| 3 | 8 | 5 | 1 | 3 | 7 | ||||||
| 4 | 8 | 5 | |||||||||
| 5 | 6 | 9 | 1 | ||||||||
| 6 | 9 | 6 | 1 | 7 | 2 | 5 | 3 | ||||
| 7 | 7 | 6 | 8 | 9 | |||||||
| 8 | 9 | 3 | 2 | 4 | 1 | 7 | |||||
| 9 | 6 | 2 | 4 | ||||||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 1 | 3 | 2 | 6 | Step 1: #1 is in Rows 1 & 3: #1 MUST go in Cell I3 | ||||||
| 2 | 2 | 7 | 1 | 4 | 8 | ||||||
| 3 | 8 | 5 | 1 | 3 | 7 | ||||||
| 4 | 1 | 8 | 5 | Step 2: #1 is in Rows 5 & 6: #1 MUST go in Cell A4 | |||||||
| 5 | 6 | 9 | 1 | (cf #1 in Column B @ B1 excludes use of Cell B4) | |||||||
| 6 | 9 | 6 | 1 | 7 | 2 | 5 | 3 | ||||
| 7 | 7 | 6 | 8 | 2 | 9 | Step 3: #2 is in Rows 8 & 9: #2 MUST go in Cell H7 | |||||
| 8 | 9 | 3 | 2 | 4 | 1 | 7 | |||||
| 9 | 6 | 2 | 4 | ||||||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 1 | 3 | 2 | 6 | Step 4: #1 is in Columns A & B: #1 MUST go in Cell C9 | ||||||
| 2 | 2 | 7 | 1 | 4 | 8 | ||||||
| 3 | 8 | 5 | 1 | 3 | 7 | ||||||
| 4 | 1 | 8 | 5 | 3 | Step 5: #3 is in Columns D & E: #3 MUST go in Cell F4 | ||||||
| 5 | 6 | 9 | 1 | ||||||||
| 6 | 9 | 6 | 1 | 7 | 2 | 5 | 3 | ||||
| 7 | 7 | 6 | 8 | 2 | 9 | Step 6: #3 is in Columns G & I: #3 MUST go in Cell H9 | |||||
| 8 | 9 | 3 | 2 | 4 | 1 | 7 | |||||
| 9 | 6 | 2 | 1 | 3 | 4 | ||||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 1 | 4 | 3 | 2 | 6 | Step 7: Complete Column F: need #s 5 & 8 | |||||
| 2 | 2 | 7 | 5 | 1 | 4 | 8 | #8 can't go in Cell F2 (cf #8 in Row 2 @ I2), so | ||||
| 3 | 8 | 5 | 1 | 3 | 7 | #8 MUST go in Cell F9, & therefore #5 MUST go in Cell F2 | |||||
| 4 | 1 | 8 | 5 | 3 | |||||||
| 5 | 3 | 6 | 9 | 1 | Step 8: Complete Column C: need #s 3 & 4 | ||||||
| 6 | 9 | 6 | 1 | 7 | 2 | 5 | 3 | #3 can't go in Cell C1 (cf #3 in Row 1 @ E1), so | |||
| 7 | 7 | 6 | 8 | 2 | 9 | #3 MUST go in Cell C5, & therefore #4 MUST go in Cell C1 | |||||
| 8 | 9 | 3 | 2 | 4 | 1 | 7 | |||||
| 9 | 6 | 2 | 1 | 8 | 3 | 4 | |||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 1 | 4 | 3 | 2 | 9 | 6 | Step 9: Block CC need #9: #9 MUST go in Cell G1 | ||||
| 2 | 2 | 7 | 5 | 1 | 4 | 8 | (cf #9 in Column I @ I7 excludes use of Cells I1 & I3) | ||||
| 3 | 8 | 5 | 1 | 3 | 7 | ||||||
| 4 | 1 | 8 | 5 | 3 | Step 10: Complete Row 6: need #s 4 & 8 | ||||||
| 5 | 3 | 6 | 9 | 1 | #8 can't go in Cell A6 (cf #8 in Column A @ A3), so | ||||||
| 6 | 4 | 9 | 6 | 1 | 8 | 7 | 2 | 5 | 3 | #8 MUST go in Cell E6, & therefore #4 MUST go in Cell A6 | |
| 7 | 7 | 6 | 8 | 2 | 9 | ||||||
| 8 | 9 | 3 | 2 | 4 | 1 | 7 | |||||
| 9 | 6 | 2 | 1 | 8 | 3 | 4 | |||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 1 | 4 | 3 | 2 | 9 | 6 | 5 | Step 11: Complete Block CC: need #s 2 & 5 | |||
| 2 | 2 | 7 | 5 | 1 | 4 | 8 | #2 can't go in Cell I1 (cf #2 in Row 1 @ F1), so | ||||
| 3 | 8 | 5 | 1 | 3 | 7 | 2 | #2 MUST go in Cell I3, & therefore #5 MUST go in Cell I1 | ||||
| 4 | 1 | 8 | 5 | 3 | 6 | ||||||
| 5 | 3 | 6 | 9 | 1 | Step 12: Complete Block II: need #s 5 & 6 | ||||||
| 6 | 4 | 9 | 6 | 1 | 8 | 7 | 2 | 5 | 3 | #6 can't go in Cell G9 (cf #6 in Row 9 @ A9), so | |
| 7 | 7 | 6 | 8 | 2 | 9 | #6 MUST go in Cell G8, & therefore #5 MUST go in Cell G9 | |||||
| 8 | 9 | 3 | 2 | 4 | 6 | 1 | 7 | ||||
| 9 | 6 | 2 | 1 | 8 | 5 | 3 | 4 | Step 13: Now #5 is in Columns G & H: #6 MUST go in Cell I4 | |||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 7 | 1 | 4 | 8 | 3 | 2 | 9 | 6 | 5 | Step 14: Complete Row 1: need #s 7 & 8 | |
| 2 | 2 | 7 | 5 | 1 | 4 | 8 | #8 can't go in Cell A1 (cf #8 in Column A @ A3), so | ||||
| 3 | 8 | 5 | 1 | 3 | 7 | 2 | #8 MUST go in Cell D1, & therefore #7 MUST go in Cell A1 | ||||
| 4 | 1 | 8 | 5 | 3 | 6 | ||||||
| 5 | 2 | 3 | 6 | 9 | 1 | Step 15: Block DD needs #2: #2 MUST go in Cell A5 | |||||
| 6 | 4 | 9 | 6 | 1 | 8 | 7 | 2 | 5 | 3 | (cf #2 in Column B @ B9 excludes use of Cells B4 & B5) | |
| 7 | 7 | 6 | 8 | 2 | 9 | ||||||
| 8 | 9 | 3 | 2 | 4 | 6 | 1 | 7 | ||||
| 9 | 6 | 2 | 1 | 8 | 5 | 3 | 4 | ||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 7 | 1 | 4 | 8 | 3 | 2 | 9 | 6 | 5 | Step 16: Complete Block DD: need #s 5 & 7 | |
| 2 | 2 | 7 | 5 | 1 | 4 | 8 | #5 can't go in Cell B4 (cf #5 in Row 4 @ Cell E4), so | ||||
| 3 | 8 | 5 | 1 | 3 | 7 | 2 | #5 MUST go in Cell B5, & therefore #7 MUST go in Cell B4 | ||||
| 4 | 1 | 7 | 8 | 5 | 3 | 9 | 6 | ||||
| 5 | 2 | 5 | 3 | 6 | 9 | 1 | Step 17: #9 is in Columns G & I: #9 MUST go in Cell H4 | ||||
| 6 | 4 | 9 | 6 | 1 | 8 | 7 | 2 | 5 | 3 | (cf #9 in Row 5 @ Cell F5 excludes use of Cell H5) | |
| 7 | 7 | 6 | 8 | 2 | 9 | ||||||
| 8 | 9 | 3 | 2 | 4 | 6 | 1 | 7 | ||||
| 9 | 6 | 2 | 1 | 8 | 5 | 3 | 4 | ||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 7 | 1 | 4 | 8 | 3 | 2 | 9 | 6 | 5 | Step 18: Complete Block EE: need #s 2 & 4 | |
| 2 | 2 | 7 | 5 | 1 | 4 | 8 | #2 can't go in Cell D5 (cf #2 in Row 5 @ Cell A5), so | ||||
| 3 | 8 | 5 | 1 | 3 | 7 | 2 | #2 MUST go in Cell D4, & therefore #4 MUST go in Cell D5 | ||||
| 4 | 1 | 7 | 8 | 2 | 5 | 3 | 4 | 9 | 6 | ||
| 5 | 2 | 5 | 3 | 4 | 6 | 9 | 8 | 1 | Step 19: Now #4 is in Rows 5 & 6: #4 MUST go in Cell G4 | ||
| 6 | 4 | 9 | 6 | 1 | 8 | 7 | 2 | 5 | 3 | ||
| 7 | 7 | 6 | 8 | 2 | 9 | Step 20: Complete Column H: #8 MUST go in Cell H5 | |||||
| 8 | 9 | 3 | 2 | 4 | 6 | 1 | 7 | ||||
| 9 | 6 | 2 | 1 | 8 | 5 | 3 | 4 | ||||
| A | B | C | D | E | F | G | H | I | |||
| 1 | 7 | 1 | 4 | 8 | 3 | 2 | 9 | 6 | 5 | Step 21: Complete Block FF: #7 MUST go in Cell G5 | |
| 2 | 9 | 2 | 7 | 5 | 1 | 4 | 8 | ||||
| 3 | 8 | 5 | 1 | 3 | 7 | 2 | |||||
| 4 | 1 | 7 | |||||||||