Implement the function to find the combination of 4 digits in a row which gives the max multiplication. If object is not a string or there are no combinations found - return nil. If combination is found - return it's multiplication result.
E.g.
max_multiplication('abc12345def') => 120 # 2*3*4*5
max_multiplication('a1b2c3d4e') => nil
Implement the function to sort array of numbers by amount of '1' in its binary representation. Numbers with identical amount of '1's should be ordered by decimal representation.
E.g.
# 3 = 11, 7 = 111, 8 = 1000, 9 = 1001.
sort([3,7,8,9]) => [8,3,9,7] # 1000, 11, 1001, 111