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Finding Prime Numbers Using The Sieve Of Eratosthenes

This program uses a simple method developed by Eratosthenes(Greek mathematician). Basically u select a number an strike of all its multiplies. then u go to the next number n so on till u reach the end. What ure left with r prime numbers.

Submitted By: Louisda16th
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Views: 10,376

Language: C
Last Modified: August 12, 2006
Instructions: compile, build n run

Snippet


  1. /* Finding Prime Numbers Using The Sieve Of Eratosthenes*/
  2. #include<stdio.h>
  3. void main()
  4. {
  5.      int num[100], i, j;
  6.      
  7.      for(i=0;i<=99;i++)     /*Fill num with the first 100 numbers*/
  8.           num[i]=i+1;
  9.      
  10.      for(i=1;i<=99;i++)
  11.      {
  12.           if(num[i]!=0)
  13.           {
  14.                for(j=(i+1);j<=99;j++)
  15.                {
  16.                     if(num[j]!=0)
  17.                     {
  18.                          if((num[j]%num[i])==0)     /*check if num[j]*/
  19.                          num[j]=0;                    /*is a multiple of num[i]*/
  20.                                                        /*if it is a multiple then set it to 0*/
  21.                     }
  22.                }
  23.           }
  24.      }
  25.  
  26.      for(i=0;i<=99;i++)
  27.      {
  28.           if(num[i]!=0)                    /*Print all non zero numbers (prime numbers)*/
  29.                printf("\n%d",num[i]);
  30.      }
  31. }
  32.  
  33.  

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