Library for hackerrank challenges

prepare_yr_library.py

""" GCD/ LCD """

# greatest common divisor
from fractions import gcd
gcd(x,y)

# least common multiple
def lcm(x, y):
    """ This function takes two
    integers and returns the L.C.M. """
    lcm = (x*y)//gcd(x,y)
    return lcm

  
""" Prime numbers """
# https://stackoverflow.com/questions/2068372/fastest-way-to-list-all-primes-below-n-in-python/3035188#3035188
def primes(n):
    """ Input n>=6, Returns a list of primes, 2 <= p < n """
    correction = (n%6>1)
    n = {0:n,1:n-1,2:n+4,3:n+3,4:n+2,5:n+1}[n%6]
    sieve = [True] * (n//3)
    sieve[0] = False
    for i in range(int(n**0.5)//3+1):
        if sieve[i]:
            k=3*i+1|1
            sieve[      ((k*k)//3)      ::2*k]=[False]*((n//6-(k*k)//6-1)//k+1)
            sieve[(k*k+4*k-2*k*(i&1))//3::2*k]=[False]*((n//6-(k*k+4*k-2*k*(i&1))//6-1)//k+1)
    return [2,3] + [3*i+1|1 for i in range(1,n//3-correction) if sieve[i]]  
  

""" Bit operations """

# bitfield
def bitfield(n):
    """ Takes an integer as input and returns a bitfield as a list""" 
    return [1 if digit=='1' else 0 for digit in bin(n)[2:]]
  
""" Strings """

# reverse a string
reverse(s)

""" Sorting """

# simple sorting
a.sort()