I was given a problem to find out all the prime numbers within a range.Just after I wrote the program I found numerous other codes to solve the problem.I am interested to know is my algorithm efficient?is it like sieve filtration?(before writing this code I had no clear idea on sieve filtration method)or the algorithm I used is a crap.:P void prime_gen(int a,int b) { int array[4]={2,3,5,7},holder[1000000]={0},count=0,flag=0,length=0,final_length=0; for(int i=0;i<b;i++) { for(int j=0;j<4;j++) { if(i==array[j]) { break; } else { if(i%array[j]==0) { count++; } } } if(count==0) { if(i>1) { holder[length++]=i; } else { length=0; } } count=0; } if(length==0) { cout<<"No prime numbers exist within the range"; cout<<"\n"; } else { cout<<"Prime numbers are:"; for(int i=0;i<length;i++) { int t=holder[i]; for(int check=0;check<length;check++) { if(t!=holder[check]) { if(t%holder[check]==0) { t=0; final_length = length-1; } else { t=t; final_length=length; } } } if(t!=0&&t>=a)cout<<t<<"\t"; } cout<<"Total count:"<<final_length<<endl; } } int main() { int a,b; cout<<"Put the first integer:"; cin>>a; cout<<"Put the second integer:"; cin>>b; prime_gen(a,b); }