4x4 hard t14d3p1.txt

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

Grid.grid1: initial copying

pending={a4, b2, c3, c4}

deduce.grid1: naked-singles

deduce.grid1. Solved.

grid1
1 2 3 4
a 1 2 4 3
b 3 4 2 1
c 4 1 3 2
d 2 3 1 4

grid1. Copying solution to raw grid.