Completed by 8.13% of challenge participants
Shifty McShuffles is hustling cards on Film Noir Island. Outwit that meddling elf and win!
Hints provided for Objective 12
- Try to outsmart Shifty by sending him an error he may not understand.
- Shifty said his deck of cards is made with Python. Surely there's a weakness to give you the upper hand in his game.
The name of this challenge almost gives the game away immediately especially when Shifty McShuffles mentions that he’s written the program in Python – we can immediately tell that this challenge will have something to do with exploiting a program by trying to pass a NaN (Not-a-Number) value.
When starting the game we are given five cards which accept a free-text input which is verified to determine that the input is a number between 0 and 9. Once all five numbers are entered we can play our hand and we compare our results with Shifty’s.
As can be expected – notwithstanding his claims to the contrary - Shify is definitely cheating and we can verify this by playing the same hand multiple times and observing that Shifty plays the same hand too which means that Shifty is able to see what cards we are going to play and modify his hand based on that.
I wasn’t quite able to figure out the algorithm Shifty is using to play his hand but through some trial and error I noticed that he always plays the 0 and 9 and that if you play 0,1,8 and 9 he will copy those and try to play the smallest possible value as the fifth number – so that a hand with 0,1,2,8,9 will force Shifty to play the exact same hand and get a tie.
Armed with the above knowledge, I tried entering nan as the input of one of the cards and sure enough it was accepted. Most probably the python code is checking whether user_input < 0 and whether user_input > 9 – both of which will return False when user_input = nan.
By playing a hand of 0, 1, 8, 9 and nan we beat Shifty every time as he tries to play 0,1,2,8,9 and nan is evaluated as being simulatenously the highest and lowest number – earning us 2 points 😊
Just re-play the same hand 5 times to win the game. Shifty may be smart but he doesn’t learn 😊
