Sieve of Eratosthenes | Python

April 26th, 2021 04:42:20 PM

					
# Given a number n, print all primes smaller than or equal to n. It is also given that n is a small number. # For example, if n is 10, the output should be “2, 3, 5, 7”. If n is 20, the output should be “2, 3, 5, 7, 11, 13, 17, 19”. # Python program to print all primes smaller than or equal to # n using Sieve of Eratosthenes def SieveOfEratosthenes(n): # Create a boolean array "prime[0..n]" and initialize # all entries it as true. A value in prime[i] will # finally be false if i is Not a prime, else true. prime = [True for i in range(n + 1)] p = 2 while (p * p <= n): # If prime[p] is not changed, then it is a prime if (prime[p] == True): # Update all multiples of p for i in range(p * 2, n + 1, p): prime[i] = False p += 1 prime[0]= False prime[1]= False # Print all prime numbers for p in range(n + 1): if prime[p]: print (p) # driver program if __name__=='__main__': n = 30 print("Following are the prime numbers smaller") print("than or equal to ", n) print("than or equal to ", n) SieveOfEratosthenes(n)

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