Flow Free Solver

Solves Flow Free puzzles.

Getting the Puzzles

Do so at your own risk.

Apple Ecosystem

download the .ipa file with iTunes

extract puzzles

 unzip -e ~/Music/iTunes/iTunes\ Media/Mobile\ Applications/Flow\ Free\ 1.7.ipa Payload/Flow.app/levelpack\*.txt

Google Ecosystem

download the .apk file

extract puzzles

 unzip -e Flow\ Free\ v2.4.apk assets/levelpack\*.txt

Data Structure

A tree of partially complete puzzle states. Each state has tile assignment (initially BLANK or WALL), a list of partial trace ends, and the number of vacant tiles.

The puzzle has a stack of untested alternatives and a list of completed boards.

Algorithm

for each segment endpoint, repeatedly look for mandatory advancement
check if it creates undesirable conditions
pick a segment endpoint with the fewest number of alternatives
try each alternative

Tricks

Patterns are translated into a JavaScript decision tree and compiled
Mandatory patterns promptly force into undesirable conditions rather than test for the potential
Puzzle and Tiles share attributes for ease of root Tiles creation
Tiles are lightweight to avoid overhead setting up each alternative
Display refresh is periodic and not a bottleneck to alternative traversal
Array splicing avoided by recycling array position
Board is represented as an one-dimensional array with walls tile assigments
Mandatory segment end extension prefers just-moved endpoint (does not increment the index)
Guesses recycle the existing Tiles to avoid one clone
Pattern results are tile offsets and are lazily used to optimize multiple guesses