Project Euler Problem 16 Statement
215 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.
What is the digit sum for the number 21000 ?
Using arbitrary–precision integer arithmetic
print (sum(map(int, str(pow(2, n)))))
Python natively supports arbitrary–precision integers and arithmetic using as many digits as there is available memory to perform a calculation. We use that feature to our full advantage to provide a simple solution to this problem.
To solve this problem we calculate 21000 (302 digits long) and convert the result to a string so we can iterate over each character–digit (integers are not iterable, but strings are).
Then, using the
map function we iterate over the string and convert every character–digit back to an integer using the
int function. Finally we calculate a digit sum by adding them together using the
HackerRank Project Euler 16 requires a little more scale by having you to solve up to 100 test cases with a higher limit of n ≤ 10,000.
Using native language arbitrary–precision structures.
Simply embrace the power of arbitrary–precision integers and ignore the call to solve it in some primitive way. It’s evolution – get use to it.
See also, Project Euler 20: Factorial digit sum