Aligned Pair Exclusion

Expert

Candidate pairs in two aligned cells are analyzed; pairs invalidated by peer constraints eliminate impossible candidates.

How It Works

For two cells in the same row, column, or box, enumerate all possible value pairs. Pairs that create conflicts with peer cells are invalid. If a candidate never appears in any valid pair for a cell, it can be eliminated.

Example

9	3	1	6	4	7	2	8	5
6	25	57	18	28	19	9	4	3
4	58	8	23	19	13	6	15	27
7	4	6	29	5	19	8	3	12
1	58	3	257	6	259	4	57	28
5	18	29	24	7	14	19	6	9
3	16	47	48	12	24	5	19	26
2	57	5	19	3	6	17	14	48
8	16	49	17	12	25	3	25	47

Key cells of the techniqueCells where elimination is appliedCandidate to be placedEliminated candidate (crossed out)

9	3	1	6	4	7	2	8	5
6	25	57	18	28	19	9	4	3
4	58	8	23	19	13	6	15	27
7	4	6	29	5	19	8	3	12
1	58	3	257	6	259	4	57	28
5	18	29	24	7	14	19	6	9
3	16	47	48	12	24	5	19	26
2	57	5	19	3	6	17	14	48
8	16	49	17	12	25	3	25	47

9	3	1	6	4	7	2	8	5
6	25	57	18	28	19	9	4	3
4	58	8	23	19	13	6	15	27
7	4	6	29	5	19	8	3	12
1	58	3	257	6	259	4	57	28
5	18	29	24	7	14	19	6	9
3	16	47	48	12	24	5	19	26
2	57	5	19	3	6	17	14	48
8	16	49	17	12	25	3	25	47

9	3	1	6	4	7	2	8	5
6	25	57	18	28	19	9	4	3
4	58	8	23	19	13	6	15	27
7	4	6	29	5	19	8	3	12
1	58	3	257	6	259	4	57	28
5	18	29	24	7	14	19	6	9
3	16	47	48	12	24	5	19	26
2	57	5	19	3	6	17	14	48
8	16	49	17	12	25	3	25	47