I have problem prime sieve code

#1

for ( ll j=ii;j<1000000;j+=i);
i did’t get the functioning of this code used in prime sieve concept
value of i is not changing so how this code is working .
in the first run when i =3 implies j=32=9 and j is then initialized to j=j+i=9+3=12
in then second run j=i*I and iis still 3 so again j will be equal to 9 so how is it running?
then in second

#2

Hi @vipuljaiswal, this for loop for (ll j=i * i;j<1000000; j+=i) is running inside another for loop which changes the value of i so, we have different value of i in each run . let me show you the snippet

for (int i=3; i *i <=1000000; i+=2) 
    { 
        // If prime[p] is not changed, then it is a prime 
        if (prime[p] == true) 
        { 
            // Update all multiples of p greater than or  
            // equal to the square of it 
            // numbers which are multiple of p and are 
            // less than p^2 are already been marked.  
            for (int j=i *i; j<=1000000; j += p) 
                prime[i] = false; 
        } 
    }

In case of any doubt feel free to ask :slight_smile:
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#3

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