4x4 Hippogonal 4902.txt

Order 2: digits 4; houses 12, cells 16.

Grid.grid1: initial copying

pending={c1, c4, d3}

deduce.grid1: naked-singles

c3 is 3 by naked-single. pending={c3}
c2 is 4 by naked-single. pending={c2}
d4 is 2 by naked-single. pending={d4}

deduce.grid1: hidden-singles

deduce.grid1: naked-pairs

two's heap=a3 {1|2}, d1 {1|3}, b3 {1|2}, b4 {3|4}, a4 {3|4}, d2 {1|3}.

Naked-pair {1|2} in cells {a3, b3} contained within {col3, box2}, updating cells {a4, b4}:

Naked-pair {3|4} in cells {a4, b4} contained within {col4, box2}, updating cells {a3, b3}:

grid1

1

2

3

4

a

1
3	4

1	2
3

1	2


3	4

b

1
3	4

1	2
3

1	2


3	4

c

2

4

3

1

d

1
3

1
3

4

2

backtrack.grid1 → grid2: a3 guess 1 ∈ {1|2}

pending={a3}

deduce.grid2: naked-singles

b3 is 2 by naked-single. pending={b3}

deduce.grid2: hidden-singles

deduce.grid2.rowa. a2 is 2 by hidden-single.

pending={a2}

deduce.grid2: naked-singles

deduce.grid2: hidden-singles

deduce.grid2: naked-pairs

two's heap=b2 {1|3}, d1 {1|3}, d2 {1|3}, b4 {3|4}, a4 {3|4}, a1 {3|4}.

grid2

1

2

3

4

a


3	4

2

1


3	4

b

1
3	4

1
3

2


3	4

c

2

4

3

1

d

1
3

1
3

4

2

backtrack.grid2 → grid3: a1 guess 3 ∈ {3|4}

pending={a1}

deduce.grid3: naked-singles

a4 is 4 by naked-single. pending={a4}
b2 is 1 by naked-single. pending={b2}
b1 is 4 by naked-single. pending={b1}
b4 is 3 by naked-single. pending={b4}
d1 is 1 by naked-single. pending={d1}
d2 is 3 by naked-single. pending={d2}

deduce.grid3. Solved.

grid3
	1	2	3	4
a	3	2	1	4
b	4	1	2	3
c	2	4	3	1
d	1	3	4	2

grid3. Copying solution to raw grid.