Statistics of the number of Eratosthenes--a method of sieve

1 Algorithmic thinking

Give the range N of the value to be sifted to find the prime number within. First use 2 to sift, that is, 2 left, the number of 2 is removed, and then the next prime, that is, 3 sieve, 3 left, the multiples of 3 were removed; then the next prime number 5 sieve, 5 left, the multiples of 5 are removed;

2 Python implementations

1  fromMathImportsqrt2  3 defcountprimes (n):4     ifNinch(0, 1, 2):    5         return06Boards = [True] *N7Boards[0] = boards[1] =False8      forIinchRange (2, int (sqrt (n)) + 1):9          forJinchRange (I *I, N, i):TenBOARDS[J] =False Oneprimes = [I forIinchBoardsifi] A     returnLen (primes)

3 Example

Statistics of the number of Eratosthenes--a method of sieve