Challenging Puzzle #44 - One Possible Solution Approach…
	NB:  There is only one final solution to this Sudoku puzzle…
	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				2		4					Challenging Puzzle #44 - November 13, 2005
2				3	9	1					Original puzzle as published © joe-ks.com
3		2	3	6		5	7
4	9	1	6				5	8
5	8								9
6		7	2					3	4
7		8	7		1		9	4
8	3		9	7		8	2		6
9				9		6
	A	B	C	D	E	F	G	H	I
1				2		4					Step 1: #3 is in Columns A & C: #3 MUST go in Cell B5...
2				3	9	1	4
3		2	3	6		5	7				Step 2: #9 is in Columns D & E: #9 MUST go in Cell F6
4	9	1	6				5	8			(#9 in Row 4 @ A4 excludes use of Cell F4, &
5	8	3							9		#9 in Row 5 @ I5 excludes use of Cell F5)
6		7	2			9		3	4
7		8	7		1		9	4			Step 3: #4 is in Column H & I: #4 MUST go in Cell G2
8	3		9	7		8	2		6		(#4 in Row 1 @ F1 excludes use of Cell G1)
9				9		6
	A	B	C	D	E	F	G	H	I
1		9		2		4					Step 4: Complete Block DD: need #s 4 & 5…
2				3	9	1	4				#4 can't go in Cell A6 (cf #4 in Row 6 @ I6), so
3		2	3	6		5	7	9			#4 MUST go in Cell C5, & therefore #5 MUST go in Cell A6
4	9	1	6				5	8
5	8	3	4						9		Step 5: #9 is in Columns A & C: #9 MUST go in Cell B1
6	5	7	2			9		3	4		(#9 in Row 2 @ E2 exludes use of Cell B2)
7		8	7		1		9	4
8	3		9	7		8	2		6		Step 6: #9 is now in Rows 1 & 2: #9 MUST go in Cell H3
9				9		6					(#9 in Column I @ I5 excludes use of Cell I3)
	A	B	C	D	E	F	G	H	I
1		9		2	7	4					Step 7: Complete Block BB: need #s 7 & 8…
2				3	9	1	4				#7 can't go in Cell E3 (cf #7 in Row 3 @ G3), so
3		2	3	6	8	5	7	9			#7 MUST go in Cell E1, & therefore #8 MUST go in Cell E3
4	9	1	6				5	8
5	8	3	4						9		Step 8: #8 is now in Columns E & F: #8 MUST go in Cell D6
6	5	7	2	8		9		3	4		(#8 in Row 4 @ H4 excludes use of Cell D4, &
7	6	8	7		1		9	4			(#8 in Row 5 @ A5 excludes use of Cell D5)
8	3		9	7		8	2		6
9				9		6					Step 9: #6 is in Rows 8 & 9: #6 MUST go in Cell A7…
	A	B	C	D	E	F	G	H	I
1		9		2	7	4					Step 10: #7 is in Columns B & C: #7 MUST go in Cell A2
2	7			3	9	1	4				(#7 in Row 1 @ E1 excludes use of Cell A1, &
3		2	3	6	8	5	7	9			(#7 in Row 3 @ G3 excludes use of Cell A3)
4	9	1	6				5	8
5	8	3	4						9
6	5	7	2	8		9		3	4
7	6	8	7		1		9	4
8	3		9	7		8	2		6
9				9		6
	A	B	C	D	E	F	G	H	I
1	1	9		2	7	4					Step 11: What possible #s can go in A1? Look at all present #s in Row 1,
2	7			3	9	1	4				Column A AND Blcok AA: #1 is the only # that can go in A1…
3		2	3	6	8	5	7	9
4	9	1	6				5	8			Step 12: #1 is now in Columns A & B: #1 MUST go in Cell C9…
5	8	3	4						9
6	5	7	2	8		9		3	4		Step 13: #1 is now in Rows 7 & 9: #1 MUST go in Cell H8…
7	6	8	7		1		9	4
8	3		9	7		8	2	1	6
9			1	9		6
	A	B	C	D	E	F	G	H	I
1	1	9		2	7	4					Step 14: Complete Column A: need #s 2 & 4…
2	7			3	9	1	4				#2 can't go in Cell A3 (cf #2 in Row 3 @ B3), so
3	4	2	3	6	8	5	7	9	1		#2 MUST go in Cell A9, & therefore #4 MUST go in Cell A3
4	9	1	6				5	8
5	8	3	4						9		Step 15: Complete Row 3: #1 MUST go in Cell I3…
6	5	7	2	8		9		3	4
7	6	8	7		1		9	4
8	3		9	7		8	2	1	6
9	2		1	9		6
	A	B	C	D	E	F	G	H	I
1	1	9		2	7	4					Step 16: Complete Row 6: need #s 1 & 6…
2	7			3	9	1	4				#1 can't go in Cell E6 (cf #1 in Column E @ E7), so
3	4	2	3	6	8	5	7	9	1		#1 MUST go in Cell G6, & therefore #6 MUST go in Cell E6
4	9	1	6				5	8
5	8	3	4				?		9		Step 17: Look at Cell G5: only one # can go in there… ???
6	5	7	2	8	6	9	1	3	4		Hint: Look at all #s in Row 5, Column G AND Block FF…
7	6	8	7		1		9	4
8	3		9	7		8	2	1	6		… #6 MUST go in Cell G5...
9	2		1	9		6
	A	B	C	D	E	F	G	H	I
1	1	9		2	7	4					Step 18: Only one # can go in Cell D4: look at all present #s in
2	7			3	9	1	4				Row 4, Column D AND Block EE…
3	4	2	3	6	8	5	7	9	1
4	9	1	6	?			5	8			Step 19: Only one # can go in Cell D7: look at all present #s in
5	8	3	4				6		9		Row 7, Column D AND Block HH…
6	5	7	2	8	6	9	1	3	4
7	6	8	7	?	1		9	4
8	3		9	7		8	2	1	6		==> #4 MUST go in D4;   #5 MUST go in D7…
9	2		1	9		6
	A	B	C	D	E	F	G	H	I
1	1	9		2	7	4					Step 20: Complete Column D: #1 MUST go in Cell D5…
2	7			3	9	1	4
3	4	2	3	6	8	5	7	9	1
4	9	1	6	4			5	8
5	8	3	4	1			6		9
6	5	7	2	8	6	9	1	3	4
7	6	8	7	5	1		9	4
8	3		9	7		8	2	1	6
9	2		1	9		6
	A	B	C	D	E	F	G	H	I
1	1	9		2	7	4					Step 21: Only one # can go in Cell I7: look at all present #s in
2	7			3	9	1	4				Row 7, Column I AND Block II…
3	4	2	3	6	8	5	7	9	1
4	9	1	6	4			5	8			Step 22: Only one # can go in Cell E8: look at all present #s in
5	8	3	4	1