Pasted my solutions to recursion problems

part-1.py

@@ -4,17 +4,42 @@
 # the appropriate comment.
 
 # factorial
-
+def factorial(n):
+ if n < 0:
+ raise ValueError("Number must be positive")
+ if n == 0:
+ return 1
+
+ return factorial(n-1) * n
 
 
 # reverse
+def reverse(text):
+ if not text or len(text) == 1:
+ return text
 
+ first = text[0]
+ last = text[-1]
+ return last + reverse(text[1:-1]) + first
 
 
 # bunny
-
+def bunny(count):
+ if not count:
+ return 0
+ if count == 1:
+ return 2
+ return bunny(count-1) + 2
 
 
 # is_nested_parens
-
+def is_nested_parens(parens):
+ if not parens:
+ return True
+ elif parens[0] == ")" or parens[-1] == "(":
+ return False
+ else:
+ is_inner_nested = parens[1:-1]
+ return is_nested_parens(is_inner_nested) 
+
 

part-2.py

@@ -4,13 +4,37 @@
 # the appropriate comment.
 
 # search
-
+def search(array, query):
+ if not array:
+ return False
+ elif array[0] == query:
+ return True
+
+ return search(array[1:], query) 
 
 
 # is_palindrome
+def is_palindrome(text):
+ if len(text) == 3 or len(text) == 2:
+ return text[0] == text[-1]
 
+ return is_palindrome(text[1:-1])
 
 
 # digit_match
+def digit_match(num_1, num_2):
+ # Base case: we're at the beginning of the num
+ if num_1 < 10 or num_2 < 10:
+ if num_1 % 10 == num_2 % 10:
+ return 1
+ else:
+ return 0
+
+ # Recursive case
+ if num_1 % 10 == num_2 % 10: 
+ return 1 + digit_match(num_1 // 10, num_2 // 10)
+ else:
+ return digit_match(num_1 // 10, num_2 // 10)
+