sieve of eratosthenes

Eratosthene method （sieve of Eratosthenes ） Used to find a certain range （n） All prime numbers in . The method is from 2 Start , stay sqrt(n) within , Remove the multiples of each prime number , The rest is the prime number of the desired range . For example, look for 100 The prime number within , The first 2 To sieve out （ Retain 2）, And then 3 To sieve out （ Retain 3）, And so on , until 7 Multiples of are sifted out （ Because the next prime number 11 Greater than sqrt(100), The rest is 100 The prime number within .