Lecture Notes on 2 August 2013

def encrypt_lowercase (ch, n):
  n = n % 26
  return (chr (ord('a') + (ord(ch) - ord ('a') + n) % 26))
 
def decrypt_lowercase (ch, n):
  n = n % 26
  return (chr (ord('z') - (ord('z') - ord(ch) + n) % 26))

def main():
  s = input ("Enter string: ")
  n = eval (input ("Enter shift: "))

  new_s = ''
  for ch in s:
    if ((ch < 'a') or (ch > 'z')):
      new_s = new_s + ch
    else:
      new_ch = encrypt_lowercase (ch, n)
      new_s = new_s + new_ch

  print (new_s)

  old_s = ''
  for ch in new_s:
    if ((ch < 'a') or (ch > 'z')):
      old_s = old_s + ch
    else:
      new_ch = decrypt_lowercase (ch, n)
      old_s = old_s + new_ch

  print (old_s)

main()


def main():
  print ('Think of a number between 1 and 100')
  lo = 1
  hi = 100
  while (lo <= hi):
    mid = (lo + hi) // 2
    response = eval (input ('You thought of ' + str(mid) + ': '))
    if (response > 0):
      hi = mid - 1
    elif (response < 0):
      lo = mid + 1
    else:
      print ('Thank you for playing the guessing game')
      return
  print ('Sorry I could not figure out')

main()



def merge (a, b):
  c = []
  idxA = 0
  idxB = 0
  while ((idxA < len(a)) and (idxB < len(b))):
    if (a[idxA] < b[idxB]):
      c.append (a[idxA])
      idxA = idxA + 1
    else:
      c.append (b[idxB])
      idxB = idxB + 1

  while (idxA < len(a)):
    c.append (a[idxA])
    idxA = idxA + 1

  while (idxB < len(b)):
    c.append (b[idxB])
    idxB = idxB + 1

  return c