Divisible by 6 or 7 but not both
I saw this student posting a problem on her blog and decided to have a go at it in Java. The problem is to print out the numbers below 100 that are divisible by either 6 or 7 but not both. The naive solution is to just loop through all the numbers below 100 and test them using the % operator. However, that might be inefficient if the limit was, say 10000000 instead of 100, so I tried to do it without using the modulus operator. It turns out that there wasn't really that significant a difference below 100000000. Ah well, here's the code anyway.

public class SixSeven{
 public static void main(String args[]){
  int adder=1;
  int six=0;
  int seven=0;
  int limit=100;
  while(six   six+=6;
   seven = six + adder;
   if(six>limit||seven>limit)
    break;
   if(adder==7){
    adder = 1;
    continue;
   }
   System.out.println(six);
   adder++;
   if(adder==7)
    continue;
   System.out.println(seven);
  }
 }
}

Labels: geek, hacking

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