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Sudoku - Diabolical — Solution #2

Difficulty: EXPERT Clues: 27 Hardest: BACKTRACKING 63 steps
0 / 63
HIDDEN SINGLE #1 R2C2 = 2 (only place for 2 in Row 2)
HIDDEN SINGLE #2 R1C6 = 2 (only place for 2 in Row 1)
HIDDEN SINGLE #3 R9C2 = 8 (only place for 8 in Row 9)
HIDDEN SINGLE #4 R9C9 = 3 (only place for 3 in Row 9)
HIDDEN SINGLE #5 R8C2 = 3 (only place for 3 in Col 2)
HIDDEN SINGLE #6 R8C4 = 6 (only place for 6 in Col 4)
HIDDEN SINGLE #7 R7C1 = 6 (only place for 6 in Row 7)
HIDDEN SINGLE #8 R6C3 = 6 (only place for 6 in Col 3)
HIDDEN SINGLE #9 R4C3 = 8 (only place for 8 in Col 3)
HIDDEN SINGLE #10 R6C7 = 9 (only place for 9 in Col 7)
HIDDEN SINGLE #11 R5C8 = 6 (only place for 6 in Col 8)
LOCKED CANDIDATES POINTING #12 7 in Box 1 → Col 1; eliminate from 1 cell(s)
LOCKED CANDIDATES CLAIMING #13 7 in Col 4 → Box 5; eliminate from 5 cell(s)
NAKED PAIR #14 R6C1 & R6C8 share {1,4}; eliminate from 7 cell(s)
NAKED SINGLE #15 R6C6 = 3 (only candidate)
NAKED SINGLE #16 R6C5 = 8 (only candidate)
HIDDEN SINGLE #17 R5C9 = 8 (only place for 8 in Row 5)
HIDDEN SINGLE #18 R5C4 = 2 (only place for 2 in Row 5)
NAKED SINGLE #19 R6C4 = 7 (only candidate)
NAKED SINGLE #20 R6C9 = 2 (only candidate)
HIDDEN SINGLE #21 R5C2 = 7 (only place for 7 in Row 5)
HIDDEN SINGLE #22 R4C9 = 7 (only place for 7 in Row 4)
SIMPLE COLORING #23 Coloring (trap): 1 — cell(s) see both colors; eliminate from 2 cell(s)
SIMPLE COLORING #24 Coloring (trap): 4 — cell(s) see both colors; eliminate from 1 cell(s)
NAKED SINGLE #25 R2C1 = 7 (only candidate)
BACKTRACKING #26 Try R1C2 = 9 (trial and error)
HIDDEN SINGLE #27 R9C1 = 9 (only place for 9 in Col 1)
NAKED SINGLE #28 R9C4 = 4 (only candidate)
NAKED SINGLE #29 R4C4 = 9 (only candidate)
XY WING #30 Pivot R8C6{1,7}, pincers R3C6 & R8C3; eliminate 4 from 1 cell(s)
SIMPLE COLORING #31 Coloring (trap): 1 — cell(s) see both colors; eliminate from 1 cell(s)
SIMPLE COLORING #32 Coloring (trap): 4 — cell(s) see both colors; eliminate from 6 cell(s)
X WING #33 4 in Cols 1,8 at Rows 3,6; eliminate from 1 cell(s)
NAKED SINGLE #34 R3C6 = 7 (only candidate)
NAKED SINGLE #35 R3C5 = 3 (only candidate)
NAKED SINGLE #36 R2C5 = 6 (only candidate)
NAKED SINGLE #37 R1C5 = 4 (only candidate)
NAKED SINGLE #38 R1C3 = 5 (only candidate)
NAKED SINGLE #39 R1C9 = 6 (only candidate)
NAKED SINGLE #40 R2C9 = 1 (only candidate)
NAKED SINGLE #41 R2C7 = 4 (only candidate)
NAKED SINGLE #42 R2C3 = 3 (only candidate)
NAKED SINGLE #43 R3C3 = 1 (only candidate)
NAKED SINGLE #44 R3C1 = 4 (only candidate)
NAKED SINGLE #45 R4C5 = 1 (only candidate)
NAKED SINGLE #46 R4C2 = 4 (only candidate)
NAKED SINGLE #47 R5C5 = 5 (only candidate)
NAKED SINGLE #48 R5C6 = 4 (only candidate)
NAKED SINGLE #49 R5C7 = 1 (only candidate)
NAKED SINGLE #50 R6C1 = 1 (only candidate)
NAKED SINGLE #51 R6C8 = 4 (only candidate)
NAKED SINGLE #52 R7C2 = 1 (only candidate)
NAKED SINGLE #53 R7C5 = 9 (only candidate)
NAKED SINGLE #54 R7C8 = 5 (only candidate)
NAKED SINGLE #55 R3C8 = 9 (only candidate)
NAKED SINGLE #56 R3C9 = 5 (only candidate)
NAKED SINGLE #57 R7C9 = 4 (only candidate)
NAKED SINGLE #58 R8C3 = 4 (only candidate)
NAKED SINGLE #59 R8C5 = 7 (only candidate)
NAKED SINGLE #60 R8C6 = 1 (only candidate)
NAKED SINGLE #61 R8C9 = 9 (only candidate)
NAKED SINGLE #62 R9C6 = 5 (only candidate)
NAKED SINGLE #63 R9C8 = 1 (only candidate)