I want to print the first 10000 prime numbers. Can anyone give me the most efficient code for this? Clarifications:
Using Sieve of Eratosthenes, computation is quite faster compare to "known-wide" prime numbers algorithm.
By using pseudocode from it's wiki (https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes), I be able to have the solution on C#.
/// Get non-negative prime numbers until n using Sieve of Eratosthenes.
public int[] GetPrimes(int n) {
if (n <= 1) {
return new int[] { };
}
var mark = new bool[n];
for(var i = 2; i < n; i++) {
mark[i] = true;
}
for (var i = 2; i < Math.Sqrt(n); i++) {
if (mark[i]) {
for (var j = (i * i); j < n; j += i) {
mark[j] = false;
}
}
}
var primes = new List();
for(var i = 3; i < n; i++) {
if (mark[i]) {
primes.Add(i);
}
}
return primes.ToArray();
}
GetPrimes(100000000) takes 2s and 330ms.
NOTE: Value might vary depend on Hardware Specifications.