/* The Sieve of Eratosthenes implemented in C#
* Robin Broad
* November 2008
* Part of a project to demonstrate an ability to
* implement an algorithm in a range of different
* computing languages and to use a range of
* compilers, including the following:
*
* Java: BlueJ
* C: Miracle C
* C++: Microsoft Visual C++.NET
* C#: Microsoft visual C#.NET
* Visual Basic: Microsoft Visual Basic.NET
*/
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace C_SharpSieve
{
class Sieve
{
public const int RANGE=1000;//we are calculating the prime numbers up to this number
static void Main()
{
//variable declarations
int[] listOfIntegers = new int[RANGE+1];//This array of integers will hold all the numbers up to the value of RANGE
int root=(int)Math.Sqrt((double)RANGE);//needed later on when removing multiples, casting is used since we're
//only interested in integer values
int product=0;//used later when removing multiples
int printCount=0;//used during print formatting of the program output
int n,multiplier=0;//used a loop counter
//initialising the integer array
for(n=1; n<=RANGE; n++)listOfIntegers[n]=n;
//starting from n=2, "remove" multiples of n up the value of RANGE
//repeat for increasing values of n up to the square root of RANGE
for(n=2; n<=root; n++)
{
//delete the multiples of n
for(multiplier=2; multiplier*n<=RANGE; multiplier++)
{
product=n*multiplier;
listOfIntegers[product]=0;
}
}//end of multiple removal
//print out the prime numbers remaining, remembering that 2 is the first prime number
System.Console.Write("The Sieve of Eratosthenes program\n");
System.Console.Write("Written in C# and compiled using Microsoft Visual C# 2008 Express\n");
System.Console.Write("Robin Broad, November 2008.\n");
System.Console.WriteLine("The prime numbers in the range: 1 to {0,4} are:-",RANGE);
for(n=2; n<=RANGE; n++)
{
//print all non-zero elements of the integer array in blocks of 10 numbers at a time
if (listOfIntegers[n]!=0)
{
System.Console.Write("{0,4}\t",listOfIntegers[n]);
printCount++;
if(printCount%10==0)System.Console.Write("\n");//every 10 items produces a new line
}
}
System.Console.WriteLine("\n\nEnd of program.\n");
}//end of main
}//end class
}//end namespace
//Robin Broad, November 2008
/*
*This program produced the following output:
The Sieve of Eratosthenes program
Written in C# and compiled using Microsoft Visual C# 2008 Express
Robin Broad, November 2008.
The prime numbers in the range: 1 to 1000 are:-
2 3 5 7 11 13 17 19 23 29
31 37 41 43 47 53 59 61 67 71
73 79 83 89 97 101 103 107 109 113
127 131 137 139 149 151 157 163 167 173
179 181 191 193 197 199 211 223 227 229
233 239 241 251 257 263 269 271 277 281
283 293 307 311 313 317 331 337 347 349
353 359 367 373 379 383 389 397 401 409
419 421 431 433 439 443 449 457 461 463
467 479 487 491 499 503 509 521 523 541
547 557 563 569 571 577 587 593 599 601
607 613 617 619 631 641 643 647 653 659
661 673 677 683 691 701 709 719 727 733
739 743 751 757 761 769 773 787 797 809
811 821 823 827 829 839 853 857 859 863
877 881 883 887 907 911 919 929 937 941
947 953 967 971 977 983 991 997
End of program.
Press any key to continue . . .
*/