// Zorah Fung, CSE 142
// An example of "fencepost" problems
public class FencepostFun {
   public static void main(String[] args) {
      printLetters("Atmosphere"); // A, t, m, o, s, p, h, e, r, e
      printLetters2("banana"); // b, a, n, a, n, a
      
      printPrimes(50);
   }
   
   // Prints out the letters of the given word with commas in between
   // NOTE: version 1. Pull out the post first
   public static void printLetters(String word) {
      System.out.print(word.charAt(0)); // (post)
      for (int i = 1; i < word.length(); i++) {
         System.out.print(", "); // (wire)
         System.out.print(word.charAt(i)); // (post)
      }
      System.out.println();
   }
   
   // NOTE: version 2. Pull out post at the end
   public static void printLetters2(String word) {
      for (int i = 0; i < word.length() - 1; i++) {
         System.out.print(word.charAt(i)); // (post)
         System.out.print(", "); // (wire)
      }
      System.out.println(word.charAt(word.length() - 1));
   }
   
   // Prints all prime numbers up to the given max, separated by commas.                                   
   public static void printPrimes(int max) {
      if (max > 1) {
         // post. We have to pull out the post first, since
         // we don't know what the last prime is
         System.out.print(2);
     
         for (int i = 3; i <= max; i++) {
            int factors = countFactors(i);
            if (factors == 2) {
               System.out.print(", " + i); // wire, post
            }
         }
         System.out.println();
      } 
   }
    
   
   // Returns the number of factors of the given integer.                                                  
   // Assumes that n >= 1.                                                                                 
   public static int countFactors(int n) {
      int count = 0;
      for (int i = 1; i <= n; i++) {
         if (n % i == 0) {
            count++;
         }
      }
      return count;
   }
}