The case notes
Count odd and even digits beside a Renban line
A Renban line holds consecutive digits in any order. On a four-cell line, that always means two odd and two even digits. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Four in a run: 2 odd, 2 even
A Renban line holds consecutive digits in any order. On a four-cell line, that always means two odd and two even digits.
Renban line claims 2 odds
Take any four neighbours in the number line: one to four, or three to six. Either way, two are odd and two are even. The purple line claims two odd places.
2 on line + 3 givens = 5 odds
A full Sudoku row has five odd digits. Three are already outside this line: five, seven and nine. With the line’s two, that accounts for all five.
r1c6 and r1c8 are even
The two other gaps, here and here, cannot be odd. Cross out one and three in both cells. They must be even, though we have not settled which even digits.
Read the transcript
A Renban line holds consecutive digits in any order. On a four-cell line, that always means two odd and two even digits. Take any four neighbours in the number line: one to four, or three to six. Either way, two are odd and two are even. The purple line claims two odd places. A full Sudoku row has five odd digits. Three are already outside this line: five, seven and nine. With the line’s two, that accounts for all five. The two other gaps, here and here, cannot be odd. Cross out one and three in both cells. They must be even, though we have not settled which even digits.
