Constraint Search and Pruning
Checking a constraint at each placement prunes whole subtrees before they are explored.
Decision · step 2 of 198Backtracking: 6 queens, the long way
Row 0, square (0, 0): no queen shares its column or a diagonal. Place a queen and move to row 1.
What you will see
The same problem with and without pruning; the pruned tree is a fraction of the size.
Cost
| Space | O(depth) |
|---|
How you work with it here
play it through, step one change at a time, scrub to any step, run it on your own input, predict what happens next.
Screen readers: Each node of the decision tree announces the choice made and whether it led to success, failure or further choices.
Reduced motion: Tree nodes appear and grey out in place; no travelling focus.
Before this
Related
Taught by the same lesson
Backtracking covers these too, in the same run.