#How It Works Code starts executing at the main method.
Opens the 100,000 digits of pi from the pi.txt as a file with read-only access. Saves to pifile variable. reads pifile into digits.
Curr_chunk is set to -1 so that if -1 is printed, there is an error.
While len(digits) >=7, use Python slicing to split into 7 digit chunks. For every 7 digit chunk, check if its both a prime and palindrome. If yes, break out of loop. Curr_chunk will not be reassigned to anything, since it broke out of loop, so curr_chunk is the answer.
Check_prime() method: I first had it checking prime using something like this method: if num > 1:
for i in range(2, num):
# If num is divisible by any number between
# 2 and n / 2, it is not prime
if (num % i) == 0:
print(num, "is not a prime number")
break
else: print(num, "is a prime number")
else: print(num, "is not a prime number")
(https://www.geeksforgeeks.org/python-program-to-check-whether-a-number-is-prime-or-not/)
However, after researching ways to optimize, I found this optimized method.
Description of optimized method:
Instead of checking till n, we can check till √n because a larger factor of n must be a multiple of smaller factor that has been already checked.
The algorithm can be improved further by observing that all primes are of the form 6k ± 1, with the exception of 2 and 3. This is because all integers can be expressed as (6k + i) for some integer k and for i = ?1, 0, 1, 2, 3, or 4; 2 divides (6k + 0), (6k + 2), (6k + 4); and 3 divides (6k + 3). So a more efficient method is to test if n is divisible by 2 or 3, then to check through all the numbers of form 6k ± 1.
Check_palindrome() method: Check palindrome first converts the parameter number into a string, and uses python slicing of strings to start from the back and go 1 character back every time to set reverse_num to the reverse of number. Then, a Boolean is returned, TRUE if reverse_num = number, FALSE if not.