Google Foobar Challenge

Level3

doomsday-fuel

• Completed in: 2 days, 19 hrs, 36 mins, 16 secs.
• Reference
  • L26.6 Absorption Probabilities, MIT OpenCourseWare

the-grandest-staircase-of-them-all

• Completed in: 16 hrs, 38 mins, 52 secs.
• DP

bomb-baby

• Completed in: 1 hr, 46 mins, 55 secs.
• GCD

Level4

running-with-bunnies

• Completed in: 1 day, 4 hrs, 40 mins, 40 secs.
• Shortest Paths

escape-pods

• Completed in: 1 day, 2 hrs, 16 mins, 11 secs.
• Minimum cut

Level5

expanding-nebula

• Completed in: 6 hrs, 49 mins, 26 secs.
• DP & Optimization

Encrypted message

CFcSBwgCCBoHRhkKU1cGAA4AGU5YQR5THBwNFwoGGAxTQQMQVBUSBg4EAAwQRhUQVBUHFAQTGRpT QQMQVBkPERkECQAWDVwXX1BGEwgJBAwCBFRVHQRGUlFBShwaDVZTGBUFVUdBShsVA1tZBwNGUlFB ShoVB1wXX1BGFAQOSklOQR5HGh5AVRY=

Extra Level

• Requested problems after level 5 clear

dodge-the-laser

• Completed in: 2 days, 20 hrs, 22 mins, 39 secs.
• References
  • Beatty sequence, Wikipedia
  • How to find A001951 A Beatty sequence: a(n)=floor(n*sqrt(2)), StackExchange
  • Beatty Sequence와 Rayleigh's theorem, blog
• Feedback

  [level5/dodge-the-lasers] (1) Some of the text readme.txt are duplicated. (2) Though the input type is string, Java input example uses quotes for string instead of double quotation marks. (3) While expected output type is string, in the output example does not use quotes. So the readers can confuse the return type.

disorderly-escape

• Completed in: 9 days, 17 hrs, 30 mins, 3 secs.
• Reference
  • Burnside's lemma: counting up to symmetries, Youtube

bringing-a-gun-to-a-trainer-fight

• Completed in: 1 day, 23 hrs, 49 mins, 54 secs.

free-the-bunny-workers

• Completed in: 3 hrs, 6 mins, 8 secs.

distract-the-trainers

• Completed in: 1 day, 23 hrs, 21 secs.
• Check Loop Proof
  1. (ac, bc) => (2ac, bc-ac) = (a, b) => (2a, b-a)
     • a < b
  2. (ac, bc+d) => (2ac, bc+d-ac) = (2ac, (b-a)c+d)
     • a < b and 0 < d < c
  3. (a, 2n-a) => (2a, 2n-2a) = (a, n-a)
     • a < n
  4. (x, y) will loop iff (x + y) % 2 == 1
     • x and y are relatively prime
• Reference
  • Maximum Matching in General Graph

prepare-the-bunnies-escape

• Completed in: 3 hrs, 17 mins, 20 secs.

find-the-access-codes

• Completed in: 1 hr, 6 mins, 52 secs.

fuel-injection-perfection

• Completed in: 1 hr, 2 secs.

queue-to-do

• Completed in: 9 hrs, 13 mins, 42 secs.

ion-flux-relabeling

• Completed in: 9 hrs, 33 mins, 36 secs.

en-route-salute

• Completed in: 7 mins, 15 secs.

power-hungry

• Completed in: 16 mins, 49 secs.

bunny-worker-locations

• Completed in: 6 mins, 49 secs.