If the message contains a pattern like ABA, then two consecutive values
will be the same. Your code generates the wrong values in this case
(because gcd = value and dividing out the gcd gives 1 instead of one of the
primes), and probably puts more than 26 values into prime_list, which leads
to alpha_id exceeding the length of alphabets later.
On Sun, Apr 7, 2019 at 5:20 PM Nicholas Sadjoli <nick.sadj...@gmail.com>
wrote:
> Hello everyone,
>
> I have tried to solve the Cryptopangram problem for the recent CodeJam,
> but I have no idea why my code is giving me a Runtime Error. The code
> already passed the sample test case, though do note that I have not tried
> with any other test cases just yet.
>
> I have analyzed for any possible mis-indent or any possible zero-division
> or mathematically invalid operations in the code. However, it is still
> producing the Runtime Error on the CodeJam interface.
>
> Any discussions for helping me understand the problem is greatly
> appreciated, and looking forward to your feedback on my code.
>
> cryptopangrams.py:
>
> import string
>
> #find GCD between 2 integers
> def gcd_euclid(n1, n2):
>
> #n2 being 0 means remainder == 0
> if n2 == 0:
> return n1
> return gcd_euclid(n2, n1 % n2)
>
> test_cases = int(input())
>
> for T in range(0, test_cases):
> N, L = map(int, input().rstrip().split(' '))
> cipher_values = list(map(int, input().rstrip().split(' ')))
>
> #get the prime numbers that make up cipher_values
> prime_list = []
> for i in range(0, L - 1):
>
> #find prime value commonly shared by current and next cipher value
> common_prime = gcd_euclid(cipher_values[i], cipher_values[i+1])
>
> #edge case for i at start of cipher_value list
> if i == 0:
> prime_list.append(int(cipher_values[i] / common_prime))
>
> prime_list.append(common_prime)
>
> #edge case for when i at end of cipher_value list
> if i == (L - 2):
> prime_list.append(int(cipher_values[i + 1] / common_prime))
>
> #get all alphabets into a string
> alphabets = string.ascii_uppercase
> alpha_id = 0
>
> #prepare dictionary for mapping between prime and alphabets
> prime_dict = {}
>
> #get a sorted prime_list first
> prime_list_sorted = sorted(prime_list.copy())
>
> #map the sorted prime numbers to the appropriate alphabets
> for p in prime_list_sorted:
> if p not in prime_dict:
> prime_dict[p] = alphabets[alpha_id]
> alpha_id += 1
>
> #Use mapping to get alphabetical values of all primes in the
> prime_list
> plaintext = ''
> for t in range(0, L + 1):
> plaintext += prime_dict[prime_list[t]]
>
> print("Case #{}: {}".format(T + 1, plaintext))
>
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