ignacy/invaders

Invaders

To run the program:

> bin/find_invaders

To run the specs:

> rspec spec

Assumptions

I had to make some assumptions about requirements/effort, here's my list:

• Ignore rotation for invaders and the radar reading, everything is matched as given
• Invaders ar hardcoded as Invaders::KNOWN_INVADERS and new ones can be added easily here
• Radar reading can be changed in toplevel radar_data file

Matching heuristic

Matching exact shapes will probably return bad results because of the possible noise. For that reason I implemented MatchStrategies The one used by the program computes the ratio of exact positional matches to all tiles for each invader.

For example:

Slice    matches    Invader

ooo-----o--    =>    --o-----o--
o--o-o-o---    =>    ---o---o---
--o-ooooo--    =>    --ooooooo--
oo--ooo-oo-    =>    -oo-ooo-oo-
ooooooo-ooo    =>    ooooooooooo
oooo--ooo-o    =>    o-ooooooo-o
o-o-----o-o    =>    o-o-----o-o
---oo-oo---    =>    ---oo-oo---

Confidence level: 0.875

MatchStrategy is expected to return match level (0-1) in the runner (Invaders::Find) I hardcoded two confidence levels to show that with the lowel level we can find multiple suspectable regions.

Example output

• High probability of a match (high threshold)

• Low probability of a match

• List of match => invader pairs