This document discusses the Sieve of Eratosthenes algorithm for finding all prime numbers below a given integer. It explains that the algorithm works by starting with a list of consecutive integers from 2 to n, and iteratively removing multiples of primes (starting from 2) until all primes below n have been found. Several examples of running the algorithm on different input values are provided. The prerequisites of loops, operators and arrays are listed, with the objective stated as understanding if-else constructs and arrays.

1. Team Emertxe
Basic Refresher

2. Assignment 12

3. Assignment 12

4. Assignment 12
WAP to print all prime numbers <= ‘num’ using Sieve of
Eratosthenes method.

5. Assignment 12
WAP to print all prime numbers <= ‘num’ using Sieve of
Eratosthenes method.
Input:

6. Assignment 12
WAP to print all prime numbers <= ‘num’ using Sieve of
Eratosthenes method.
Input: Read integer ‘num’

7. Assignment 12
WAP to print all prime numbers <= ‘num’ using Sieve of
Eratosthenes method.
Input: Read integer ‘num’
Output:

8. Assignment 12
WAP to print all prime numbers <= ‘num’ using Sieve of
Eratosthenes method.
Input: Read integer ‘num’
Output: Print the prime numbers less than or equal to ‘num’

9. Assignment 12
What is a Prime number?

10. Assignment 12
What is a Prime number?
 A number that is divisible only by itself and 1.

11. Assignment 12
What is a Prime number?
 A number that is divisible only by itself and 1.
 Examples: 2, 3, 5, 7, 11 etc.

12. Assignment 12
Sieve of Eratosthenes:-

13. Assignment 12
Sieve of Eratosthenes:-
⮚The sieve of Eratosthenes is one of the most efficient ways to
find all of the smaller primes.

14. Assignment 12
Sieve of Eratosthenes:-
⮚The sieve of Eratosthenes is one of the most efficient ways to
find all of the smaller primes.
⮚Generate a list of integers from 2 to 20

15. Assignment 12
Sieve of Eratosthenes:-
⮚The sieve of Eratosthenes is one of the most efficient ways to
find all of the smaller primes.
⮚Generate a list of integers from 2 to 20
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

16. Assignment 12
Sieve of Eratosthenes:-
⮚The sieve of Eratosthenes is one of the most efficient ways to
find all of the smaller primes.
⮚Generate a list of integers from 2 to 20
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

17. Assignment 12
Sieve of Eratosthenes:-
⮚The first number in the list is 2; cross out every multiples of
2.

18. Assignment 12
Sieve of Eratosthenes:-
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X
i
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

19. Assignment 12
Sieve of Eratosthenes:-
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X X
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

20. Assignment 12
Sieve of Eratosthenes:-
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X X X
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

21. Assignment 12
Sieve of Eratosthenes:-
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X X X
X X
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

22. Assignment 12
Sieve of Eratosthenes:-
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X X X
X X X
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

23. Assignment 12
Sieve of Eratosthenes:-
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X X X
X X X X
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

24. Assignment 12
Sieve of Eratosthenes:-
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X X X
X X X X X
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

25. Assignment 12
Sieve of Eratosthenes:-
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X X X
X X X X X X
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

26. Assignment 12
Sieve of Eratosthenes:-
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X X X
X X X X X X X
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

27. Assignment 12
Sieve of Eratosthenes:-
⮚ Can we remove array elements?

28. Assignment 12
Sieve of Eratosthenes:-
⮚ Can we remove array elements?
We cannot remove array elements

29. Assignment 12
Sieve of Eratosthenes:-
⮚ Can we remove array elements?
We cannot remove array elements
⮚What can be done?

30. Assignment 12
Sieve of Eratosthenes:-
⮚ Can we remove array elements?
We cannot remove array elements
⮚What can be done?
Make it as 0

31. Assignment 12
Sieve of Eratosthenes:-
⮚ Can we remove array elements?
We cannot remove array elements
⮚What can be done?
Make it as 0
2 3 0 5 0 7 0 9 0 11 0 13 0 15 0 17 0 19 0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

32. Assignment 12
Sieve of Eratosthenes:-
⮚The next number in the list is 3, make multiples of 3 as 0
2 3 0 5 0 7 0 9 0 11 0 13 0 15 0 17 0 19 0
i
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

33. Assignment 12
Sieve of Eratosthenes:-
⮚ The next number in the list is 3, make multiples of 3 as 0
2 3 0 5 0 7 0 0 0 11 0 13 0 15 0 17 0 19 0
i
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

34. Assignment 12
Sieve of Eratosthenes:-
⮚ The next number in the list is 3, make multiples of 3 as 0
2 3 0 5 0 7 0 0 0 11 0 13 0 0 0 17 0 19 0
i
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

35. Assignment 12
Sieve of Eratosthenes:-
⮚The next number which is not removed is 5.
2 3 0 5 0 7 0 0 0 11 0 13 0 0 0 17 0 19 0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

36. Assignment 12
Sieve of Eratosthenes:-
⮚ The next number which is not removed is 5.
⮚It is not necessary to remove multiples of 5, because all non
prime numbers has been removed.
2 3 0 5 0 7 0 0 0 11 0 13 0 0 0 17 0 19 0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
i

37. ⮚Print all the non-zero numbers from the list.
Assignment 12
Sieve of Eratosthenes:-
2 3 0 5 0 7 0 0 0 11 0 13 0 0 0 17 0 19 0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

38. ⮚Prime numbers are:
2, 3, 5, 7, 11, 13, 17, 19
Assignment 12
Sieve of Eratosthenes:-

39. Assignment 12
Example’s:

40. Assignment 12
Example’s:
⮚Input:

41. Assignment 12
Example’s:
⮚Input: num = 20

42. Assignment 12
Example’s:
⮚Input: num = 20
Output:

43. Assignment 12
Example’s:
⮚Input: num = 20
Output: 2, 3, 5, 7, 11, 13, 17, 19

44. Assignment 12
Example’s:
⮚Input: num = 20
Output: 2, 3, 5, 7, 11, 13, 17, 19
⮚Input:

45. Assignment 12
Example’s:
⮚Input: num = 20
Output: 2, 3, 5, 7, 11, 13, 17, 19
⮚Input: num = 30

46. Assignment 12
Example’s:
⮚Input: num = 20
Output: 2, 3, 5, 7, 11, 13, 17, 19
⮚Input: num = 30
Output:

47. Assignment 12
Example’s:
⮚Input: num = 20
Output: 2, 3, 5, 7, 11, 13, 17, 19
⮚Input: num = 30
Output: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29

48. Assignment 12
Example’s:
⮚Input: num = 20
Output: 2, 3, 5, 7, 11, 13, 17, 19
⮚Input: num = 30
Output: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29
⮚Input:

49. Assignment 12
Example’s:
⮚Input: num = 20
Output: 2, 3, 5, 7, 11, 13, 17, 19
⮚Input: num = 30
Output: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29
⮚Input: num = -20

50. Assignment 12
Example’s:
⮚Input: num = 20
Output: 2, 3, 5, 7, 11, 13, 17, 19
⮚Input: num = 30
Output: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29
⮚Input: num = -20
Output:

51. Assignment 12
Example’s:
⮚Input: num = 20
Output: 2, 3, 5, 7, 11, 13, 17, 19
⮚Input: num = 30
Output: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29
⮚Input: num = -20
Output: Please enter a positive number which is > 1

52. Sample execution:-
Assignment 12

53. Sample execution:-
Assignment 12

54. Sample execution:-
Assignment 12

55. Assignment 12
Pre-requisites:-

56. Assignment 12
Pre-requisites:-
⮚Loops

57. Assignment 12
Pre-requisites:-
⮚Loops
⮚Operators

58. Assignment 12
Pre-requisites:-
⮚Loops
⮚Operators
⮚Arrays

59. Assignment 12
Pre-requisites:-
⮚Loops
⮚Operators
⮚Arrays
Objective:-

60. Assignment 12
Pre-requisites:-
⮚Loops
⮚Operators
⮚Arrays
Objective:-
⮚To understand the concept of if-else constructs and arrays.

61. Team Emertxe
Thank you