quiz.md

CSE 143

Quiz

Week 5

1. Recursive Tracing

   public static String mystery (String s, char c) {
   	if (s.length() == 0) {
   		return s;		
   	} else if (s.charAt(s.length() - 1) == c) {
   		return c + mystery(s.substring(0, s.length() - 1), c);
   		
   	} else {
   		int len =  s.length() - 1;
   		return mystery(s.substring(0, len), c) + s.charAt(len);
   	}
   }

   Call	Output
   mystery("sce", 'c');
   mystery("static", 't');
   mystery("banana", 'a');
   mystery("java", 'j');
   mystery("ALL", 'L');

2. Write what the method returns, given the specified inputs. If the method will enter an infinite recursion, say "infinite recursion".

   public static String mystery(int x, int y) {
       if(x == y)
           return "!";
       if(x == y + 1)
           return "**";
       return mystery(x + 1, y) + mystery(x + 2, y);
   }

   Call	Output
   mystery(6,5);
   mystery(-5,-4)
   mystery(3,1)
   mystery(4,6)
   mystery(3,6)