I have watched the videos from mycodeschool and implemented it:
code:
//find all prime numbers upto n
//sieve of erastosthenes
#include<bits/stdc++.h>
int main()
{
int n;
scanf("%d",&n);
int primes[n];
for(int i=0; i<=n; i++)
{
primes[i]=1; //make prime to all numbers between 0 and n
}
primes[0]=0; //0 not prime
primes[1]=0; //1 not prime
for(int i=2; i<=n; i++) //2 to n iterating
{
if(primes[i]==1) //if 2 to n is prime then
{
for(int j=2; i*j<=n; j++) //j=2 and i*j<=9 means 2*2<=9
{
primes[i*j]=0; //primes[i*j=2*2=4] means primes[4]=0;
}
printf("%d ",i); //
}
}
}
Video:
