### Sieve of Eratoshenes

A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself.

I want to find Prime number from 2, 3, .... To N

First we need to make

new int [N];

like this ~ we visit all number of Array.

below is my code

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | /** * 1== prime * * @return */ public static int[] isPrimeFromSieve(int limit) { int[] val = new int[limit]; for (int i = 2; i < val.length; i++) { if (val[i] == 0) { val[i] = 1; checkMultiple(i, val); } } return val; } private static void checkMultiple(int a, int[] val) { for (int i = 2; i < val.length; i++) { int num = a * i; if (num >= val.length) { return; } val[num] = 2; } } |

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