为什么我的Eratosthenes筛网会除去非素数？

Question

My code:

def sieve(list1):

    not_prime = set()
    primes = []
    for i in range(2, list1+1):
        if i in not_prime:
            continue
        for x in range(i*2, list1+1, i):
            not_prime.add(x)
        primes.append(i)
    return primes

I am trying to keep the non-prime numebrs and change it to 0. Where am I going wrong? The output doesn't even show any other number besides the prime numbers.

Answer 1

Well in that case, cant you just append zero instead of continue in the no_prime clause?

def sieve(list1):
    not_prime = set()
    primes = []
    for i in range(2, list1+1):
        if i in not_prime:
            primes.append(0);
            continue;
        for x in range(i*2, list1+1, i):
            not_prime.add(x)
        primes.append(i)
    return primes



sieve(27)

# output [2, 3, 0, 5, 0, 7, 0, 0, 0, 11, 0, 13, 0, 0, 0, 17, 0, 19, 0, 0, 0, 23, 0, 0, 0, 0]

Or if this is anything beyond a toy, you probably want to look into sparse arrays.