http://play.websudoku.com/?level=4&set_id=6272704798 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 . . | b | 7 . 3 | . . . | . . . | c | . 5 . | . . . | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | . . . | e | . 3 . | 7 . 1 | . 4 . | f | . . . | . . 9 | 5 8 . | +-------+-------+-------+ g | . 7 8 | . . . | . 2 . | h | . . . | . . . | 4 . 7 | i | . . 6 | . . 2 | . . . | +-------+-------+-------+ Row e: e5 = 8 Row f: f9 = 1 Row f: f3 = 7 Row i: i5 = 7 Column 7: d7 = 7 Block 3: a8 = 7 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | . . . | c | . 5 . | . . . | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 . . | e | . 3 . | 7 8 1 | . 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 . | h | . . . | . . . | 4 . 7 | i | . . 6 | . 7 2 | . . . | +-------+-------+-------+ Row c: c6 = 7 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | . . . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 . . | e | . 3 . | 7 8 1 | . 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 . | h | . . . | . . . | 4 . 7 | i | . . 6 | . 7 2 | . . . | +-------+-------+-------+ Field b8 can only have value 5 Field e7 can only have value 2 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | . 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 . . | e | . 3 . | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 . | h | . . . | . . . | 4 . 7 | i | . . 6 | . 7 2 | . . . | +-------+-------+-------+ Field b7 can only have value 8 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 . . | e | . 3 . | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 . | h | . . . | . . . | 4 . 7 | i | . . 6 | . 7 2 | . . . | +-------+-------+-------+ Column 9: i9 = 8 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 . . | e | . 3 . | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 . | h | . . . | . . . | 4 . 7 | i | . . 6 | . 7 2 | . . 8 | +-------+-------+-------+ Row i: i1 = 5 Column 9: g9 = 5 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 . . | e | . 3 . | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 5 | h | . . . | . . . | 4 . 7 | i | 5 . 6 | . 7 2 | . . 8 | +-------+-------+-------+ Row e: e3 = 5 Block 9: h8 = 6 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 . . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 5 | h | . . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | . . 8 | +-------+-------+-------+ Block 9: i8 = 9 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 . . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 5 | h | . . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | . 9 8 | +-------+-------+-------+ Column 8: d8 = 3 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 5 | h | . . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | . 9 8 | +-------+-------+-------+ Column 3 requires value 4 in Block 1 Block 4 requires value 9 in Column 1 Block 7 requires value 9 in Row h 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 5 | h | . . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | . 9 8 | +-------+-------+-------+ Matching fields in Column 6: only ['b6', 'd6'] can contain [4, 6] 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . . | . 2 5 | h | . . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | . 9 8 | +-------+-------+-------+ Field g6 can only have value 3 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . 3 | . 2 5 | h | . . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | . 9 8 | +-------+-------+-------+ Row h: h1 = 3 Row i: i7 = 3 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . 3 | . 2 5 | h | 3 . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | 3 9 8 | +-------+-------+-------+ Column 7: g7 = 1 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | . . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . 3 | 1 2 5 | h | 3 . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | 3 9 8 | +-------+-------+-------+ Column 1: a1 = 1 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | 1 . . | 2 . . | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | . 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . 3 | 1 2 5 | h | 3 . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | 3 9 8 | +-------+-------+-------+ Row a: a6 = 8 Column 1: c1 = 8 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | 1 . . | 2 . 8 | 6 7 . | b | 7 . 3 | . . . | 8 5 . | c | 8 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . 3 | 1 2 5 | h | 3 . . | . . . | 4 6 7 | i | 5 . 6 | . 7 2 | 3 9 8 | +-------+-------+-------+ Row a: a5 = 5 Row h: h4 = 8 Column 6: h6 = 5 Block 1: b2 = 6 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | 1 . . | 2 5 8 | 6 7 . | b | 7 6 3 | . . . | 8 5 . | c | 8 5 . | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . . | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . 3 | 1 2 5 | h | 3 . . | 8 . 5 | 4 6 7 | i | 5 . 6 | . 7 2 | 3 9 8 | +-------+-------+-------+ Row a: a9 = 3 Row b: b9 = 2 Column 6: d6 = 6 Block 1: c3 = 2 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | 1 . . | 2 5 8 | 6 7 3 | b | 7 6 3 | . . . | 8 5 2 | c | 8 5 2 | . . 7 | 9 1 . | +-------+-------+-------+ d | . 8 1 | 5 . 6 | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 . | f | . . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . 3 | 1 2 5 | h | 3 . . | 8 . 5 | 4 6 7 | i | 5 . 6 | . 7 2 | 3 9 8 | +-------+-------+-------+ Row a: a3 = 4 Row f: f1 = 6 Row h: h2 = 2 Column 6: b6 = 4 Column 9: c9 = 4 Column 9: e9 = 6 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | 1 . 4 | 2 5 8 | 6 7 3 | b | 7 6 3 | . . 4 | 8 5 2 | c | 8 5 2 | . . 7 | 9 1 4 | +-------+-------+-------+ d | . 8 1 | 5 . 6 | 7 3 . | e | . 3 5 | 7 8 1 | 2 4 6 | f | 6 . 7 | . . 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . 3 | 1 2 5 | h | 3 2 . | 8 . 5 | 4 6 7 | i | 5 . 6 | . 7 2 | 3 9 8 | +-------+-------+-------+ Row a: a2 = 9 Row e: e1 = 9 Row f: f5 = 2 Row h: h5 = 1 Row h: h3 = 9 Column 1: d1 = 2 Column 2: i2 = 1 Column 9: d9 = 9 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | 1 9 4 | 2 5 8 | 6 7 3 | b | 7 6 3 | . . 4 | 8 5 2 | c | 8 5 2 | . . 7 | 9 1 4 | +-------+-------+-------+ d | 2 8 1 | 5 . 6 | 7 3 9 | e | 9 3 5 | 7 8 1 | 2 4 6 | f | 6 . 7 | . 2 9 | 5 8 1 | +-------+-------+-------+ g | . 7 8 | . . 3 | 1 2 5 | h | 3 2 9 | 8 1 5 | 4 6 7 | i | 5 1 6 | . 7 2 | 3 9 8 | +-------+-------+-------+ Row b: b4 = 1 Row d: d5 = 4 Row f: f4 = 3 Row i: i4 = 4 Column 1: g1 = 4 Column 2: f2 = 4 Column 5: c5 = 3 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | 1 9 4 | 2 5 8 | 6 7 3 | b | 7 6 3 | 1 . 4 | 8 5 2 | c | 8 5 2 | . 3 7 | 9 1 4 | +-------+-------+-------+ d | 2 8 1 | 5 4 6 | 7 3 9 | e | 9 3 5 | 7 8 1 | 2 4 6 | f | 6 4 7 | 3 2 9 | 5 8 1 | +-------+-------+-------+ g | 4 7 8 | . . 3 | 1 2 5 | h | 3 2 9 | 8 1 5 | 4 6 7 | i | 5 1 6 | 4 7 2 | 3 9 8 | +-------+-------+-------+ Row b: b5 = 9 Row c: c4 = 6 Column 4: g4 = 9 Column 5: g5 = 6 1 2 3 4 5 6 7 8 9 +-------+-------+-------+ a | 1 9 4 | 2 5 8 | 6 7 3 | b | 7 6 3 | 1 9 4 | 8 5 2 | c | 8 5 2 | 6 3 7 | 9 1 4 | +-------+-------+-------+ d | 2 8 1 | 5 4 6 | 7 3 9 | e | 9 3 5 | 7 8 1 | 2 4 6 | f | 6 4 7 | 3 2 9 | 5 8 1 | +-------+-------+-------+ g | 4 7 8 | 9 6 3 | 1 2 5 | h | 3 2 9 | 8 1 5 | 4 6 7 | i | 5 1 6 | 4 7 2 | 3 9 8 | +-------+-------+-------+