CODEWITHSUNDEEP
pythonnumberssieve-algorithm
Ahy
Ahy

Reputation: 15

Lucky Numbers in Python

For who's interested in; lucky numbers are generated by eliminating numbers based on their position in the set. i.e:

1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22

First eliminates every second number bc second value is 2:

1,3,5,7,9,11,13,15,17,19,21

First remaining number in the list after 1 is 3; so it eliminates every third number:

1,3,7,9,13,15,17,19,21

Next number is 7; eliminate every 7th number in the list:

1,3,7,9,13,15,21

Next surviving nunmber after 7 is 9 but obviously there are not enough numbers to eliminate. For further information you can check Lucky Number

So, if my list doesn't contain any negative number and begins with 1 i.e:

    numbers = ['1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20', '21', '22']

My code supposed to delete every number unless it's a lucky number, so I tried:

    def lucky_numbers(numbers):
        del numbers[::-2]   # Delete even numbers
        while int(numbers[1]) < len(numbers):
            x = int(numbers[1])
            del numbers[-1::x]
            print(numbers)
            return
        return
    lucky_numbers(numbers)

But it returns:

['1', '3', '5', '7', '9', '11', '13', '15', '17', '19']

Where am I wrong? Or is there any efficient way to write it? Thank you.

Upvotes: 0

Views: 4044

Answers (1)

sai
sai

Reputation: 1784

The negative index is a bit confusing to me (at least), see if this code is easy to interpret-

numbers = ['1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20', '21', '22']

def lucky_numbers(numbers):
    index = 1
    next_freq = int(numbers[index])
    while int(next_freq) < len(numbers):
        del numbers[next_freq-1::next_freq]
        print(numbers)
        if str(next_freq) in numbers:
            index += 1
            next_freq = int(numbers[index])
        else:
            next_freq = int(numbers[index])
    return


lucky_numbers(numbers)

['1', '3', '5', '7', '9', '11', '13', '15', '17', '19', '21']
['1', '3', '7', '9', '13', '15', '19', '21']
['1', '3', '7', '9', '13', '15', '21']

Upvotes: 1

Related Questions