palindrome

README.md

@@ -4,6 +4,11 @@ Write a method factorial that accepts an integer parameter n and that uses recur
 
 ## fib(n)
 Write a method fib that accepts an integer n as a parameter and returns the nth fibonacci number.
+fib(4) = 3
+1 1 3 5 8 13
+fib(1) == 1
+fib(2) == 1
+
 
 ## pal(s)
 Write a method pal that accepts a string s as a parameter and returns a boolean value indicating if that string is a palindrome or not.

recursion.rb

@@ -1,14 +1,46 @@
-
 def fact(n)
+  if n == 0 || n == 1
+    return 1
+  end
+
+  return n * fact(n-1)
 end
 
 def fib(n)
+  if n == 1 || n == 2
+    return 1
+  end
+
+  return fib(n-1) + fib(n-2)
 end
 
 def pal(s)
+  if s.length == 0 || s.length == 1
+    return true
+  end
+
+  if s.chars[0] == s.chars[s.length-1]
+    s.slice!(0)
+    s.slice!(s.length-1)
+    pal(s)
+  else
+    return false
+  end
 end
 
 def binary(n)
+  binary_helper(n)
+end
+
+def binary_helper(digits, binary="", result="")
+  if digits == 0
+    result += binary + " "
+    return result
+  else
+    result = binary_helper(digits-1,binary+"0", result)
+    result = binary_helper(digits-1,binary+"1", result)
+  end
+  return result
 end
 
 def travel(x,y)