How to solve Queens
Start at the smallest regions. Cross out what they own, test the cells that touch them, and place a queen wherever only one cell is left.
How it works
Queens has three moves, and you repeat them until the board is full.
One: find a region that fits inside one row or column. It owns that line’s queen, so cross out the rest of the line. Two: test cells beside small regions. If a queen there would touch every open cell of a region, cross it out. Three: when a row, column or region has one open cell left, its queen goes there. Cross out everything the new queen rules out.
You never need to guess. Every Queens board here has a unique solution that these steps reach.
Where to look first
Small regions and regions along an edge have the fewest options, so they give the first deductions. A region of one cell is a free queen.
After each queen, look at the regions next to it. They just lost cells, and one may now fit in a single line.
Worth memorizing
Small regions first.
They fit in one line most often.
Owned line: cross out the rest.
A region inside one row owns that row’s queen.
Touching test: would it empty a region?
Then the cell is out.
Practice
0 of 4 rightOn the empty board, which two regions each fit inside one line?
A queen on which of these cells would leave region E with no room?
Where does row 6’s queen go?
With F’s queen placed, region D fits inside one line. Which?