recursion programs to try

Try writing these recursion functions. Include a main() program that calls and tests the recursive function!

• sum all values in a list: sumList(L)

  L:  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  sumList(L):  45
  
  
  L:  [2, 4, 6, 8]
  sumList(L):  20
  

• determine if given string is a palindrome or not: isPalindrome(s)

  string: racecar
  palindrome!
  
  
  string: we love CS
  NOT a palindrome...
  

• determine if given list is sorted or not: isSorted(L)

  L:  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  isSorted(L):  True
  
  
  L:  [9, 4, 60, 8]
  isSorted(L):  False
  

• draw concentric circles, given initial center and size: circles(cp, size, win)

• replace all instances of ch in string s with new: replace(s, ch, new)

  string: we love computer science!
      ch: e
     new: 3
          w3 lov3 comput3r sci3nc3!
  
  
  string: mississippi
      ch: i
     new: PONY
          mPONYssPONYssPONYppPONY
  

• return a list with n identical items in it: xerox(item, n)

  xerox('pony', 4):  ['pony', 'pony', 'pony', 'pony']
  xerox(3.14, 6):  [3.14, 3.14, 3.14, 3.14, 3.14, 3.14]
  

Hint: you can add two lists together:

    >>> L1 = ['pony']
    >>> L2 = ['horse']
    >>> L1 + L2
    ['pony', 'horse']

• multiply all values in a list: multiplyList(L)

  L:  [2, 3, 4, 5]
  multiplyList(L):  120
  
  
  L:  [237, 0, 138, 407]
  multiplyList(L):  0
  

• find the largest item in a list: recmax(L)

  L:  [0, 8, 4, 5, 6, 3, 1, 2, 9, 7]
  recmax(L):  9
  L:  [200, 44, 321, -8]
  recmax(L):  321
  

• get valid input from user -- get an integer: getInt()

  integer: 5.0
  integer: pony
  integer: 4 4
  integer: 16
  16
  

(keep asking until you get an integer)

• draw sets of four circles using recursion: fourcircles(cp, size, win)

recursion is fun! :)