#            CSC 15 Basic Practice Problems

#  Sample solutions will be given to you when you turn in your attempts.
#  You will be given credit for a problem as long as you showed serious
#  attempt at solving it yourself.  Test your solutions in Python (make
#  sure you can call the function too).
#######################################


#0a Write code to construct a list containing all the numbers that are
#   evenly divisible by 8 from 0 to 10000, i.e., the list
#   [0,8,16,24,32,40,48,56,64, ... 10000].  Hint: first line is
M = []


#0b. Write a function 'product' that multiplies all numbers in an array.
#   For example, product([3,2,5]) should return 30.  Hint: the product
#   of the empty array is 1.  hint: don't multiply by i, multiply by A[i]!!
#   Think clearly: are you refering to the index or the element.
def prod(A):  # A is the list passed in when the function is called.


#1. Write a function 'doubles' that takes a list as parameter and constructs
#   a new list with two copies of each element of the parameter list.
#   For example, doubles([2,4,6,8]) should return [2,2,4,4,6,6,8,8].  Hint:
#   inside the loop, do two appends.


#2. Write a function to reverse a list.  That is, reverse([2,4,6,8]) should
#   construct and return the list [8,6,4,2]


#3a. Write a function h that returns True iff there is a number greater than 
#  100 in a list.  For example, h([4,6,1,109,3]) should return True.  It 
#  should return False otherwise.


#3b Write a function h2 that returns True iff there is at least 2 numbers
#  in the given list that's greater than 100.  For example, h2([4,6,1,109,3])
#  should return False, and h2([45,180,21,346,12]) should return True


#4 Write a nested loop that prints

X X X X X
X X X X
X X X
X X
X

# The outer loop should run 5 times.  The inner loop prints each line.


#5. Write a function 'odds' that takes an array as an argument and returns
#   and array containing all the odd numbers of the given array.  For
#   example, odds([4,3,6,8,1,9]) should return [3,1,9], which are all the
#   odd numbers of the given (parameter) list.  hint: start with an empty
#   list, then append all the odd numbers you find to the list.  A number
#   is odd if its remainder after dividing by 2 is 1.


#6 write a function sublist(A,B) that returns True iff every element of
#  A also appears in B.  For example, sublist([2,4,6], [1,2,3,4,5,6,7])
#  should return True. (implicitly returns False if A is not a sublist of B)
#  hint: the expression (x in B) is True iff x occurs in array B


#7 (similar) write a function intersection(A,B) that returns the
#  intersection of the lists A, B.  That is, it should return a list M
#  that contains all elements that are in both A and B. Duplicates are
#  fine.  For example, intersection([2,4,6,8], [1,2,3,4,5]) should
#  return [2,4], which is the intersection of the two lists.  Hint:
#  you don't need a nested loop.  All you have to do is to go through
#  the list A and look for the elements that are also in B.


#8 write a function 'occurs(x,A)' that returns the first index in A where
#  x is found.  If x does not exist in A, then the function should return
#  -1


# write a function count that returns the number of times x occurs in A.
# for example, count(3,[4,3,7,3,1]) should return 2
#

# (harder)  a permutation is a list of length n that contains the numbers
# 0 to n-1.  For example, [4,2,0,1,3] is a permutation of length 5.  It
# permutes the numbers 0 to 4.  That is, 4 becomes 0, 2 becomes 1, 0 becomes 2,
# etc.  Now we can use a permutation to permute or "scramble" a string of
# the same length, such as "hello" by applying the permutation to each
# character.  Applying the above permutation list to "hello" will result
# in "olhel":
#hello
#01234
#olhel