INDEX

Problem 1

Find the last element of a list.

[1 2 3 7 5] -> 5


Problem 2

Find the last but one element of a list.

[1 2 3 7 5] -> 7


Problem 3

Find the K’th element of a list

The first element in the list is number 1.

[1 2 3 7 5] 4 -> 7


Problem 4

Find the number of elements of a list.

[1 2 3 5 7] -> 5


Problem 5

Reverse a list.

[1 2 3 7 5] -> [5 7 3 2 1]


Problem 6

Find out whether a list is a palindrome.

A palindrome can be read forward or backward.

[1 2 3 3 2 1] -> true


Problem 7

Flatten a nested list structure.

Transform a list, possibly holding lists as elements into a `flat’ list by replacing each list with its elements (recursively).

[1 [2 3 [5 7] 3] 1] -> [1 2 3 5 7 3 1]


Problem 8

Eliminate consecutive duplicates of list elements.

If a list contains repeated elements they should be replaced with a single copy of the element. The order of the elements should not be changed.

[1 1 1 2 2 3 1 5 5 3 3] -> [1 2 3 1 5 3]


Problem 09

Pack consecutive duplicates of list elements into sublists.

If a list contains repeated elements they should be placed in separate sublists.

[1 1 1 2 2 3 1 5 5 3 3] -> [[1 1 1] [2 2] [3] [1] [5 5] [3 3]]


Problem 10

Run-length encoding of a list.

Use the result of problem 9 to implement the so-called run-length encoding data compression method. Consecutive duplicates of elements are encoded as terms (N E) where N is the number of duplicates of the element E.

[1 1 1 2 2 3 1 5 5 3 3] -> [(3 1) (2 2) (1 3) (1 1) (2 5) (2 3)]


Problem 11

Modified run-length encoding.

Modify the result of problem 10 in such a way that if an element has no duplicates it is simply copied into the result list. Only elements with duplicates are transferred as (N E) terms.


Problem 12

Decode a run-length encoded list.

Given a run-length code list generated as specified in problem 11. Construct its uncompressed version.

[(3 1) (2 2) 3 1 (2 5) (2 3)] -> [1 1 1 2 2 3 1 5 5 3 3]


Problem 13

Run-length encoding of a list (direct solution).

Implement the so-called run-length encoding data compression method directly. I.e. don’t explicitly create the sublists containing the duplicates, as in problem 9, but only count them. As in problem 11, simplify the result list by replacing the singleton terms (1 X) by X.

[1 1 1 2 2 3 1 5 5 3 3] -> [(3 1) (2 2) 3 1 (2 5) (2 3)]


Problem 14

Duplicate the elements of a list.

[1 2 3 1] -> [1 1 2 2 3 3 1 1]


Problem 15

Replicate the elements of a list a given number of times.

[1 2 3 1] 3 -> [1 1 1 2 2 2 3 3 3 1 1 1]


Problem 16

Drop every N`th element from a list.

[1 2 3 4 5 6 7 8] 3 -> [1 2 4 5 7 8]


Problem 17

Split a list into two parts; the length of the first part is given.

Do not use any predefined predicates.

[1 2 3 4 5 6 7 8] 3 -> ([1 2 3] [4 5 6 7 8])


Problem 18

Extract a slice from a list.

Given two indices, I and K, the slice is the list containing the elements between the I`th and K`th element of the original list (both limits included). Start counting the elements with 1.


Problem 19

Rotate a list N places to the left.

[1 2 3 4 5 6 7 8] 3 -> [4 5 6 7 8 1 2 3]


Problem 20

Remove the K`th element from a list.

[1 2 3 4] 2 -> (2, [1 3 4])


Problem 21

Insert an element at a given position into a list.

[1 2 3 4] 2 5 -> [1 5 2 3 4]


Problem 22

Create a list containing all integers within a given range.

(4 9) -> [4 5 6 7 8 9]


Problem 23

Extract a given number of randomly selected elements from a list.

[1 2 3 4 5 6 7 8] 3 -> [7 3 5]


Problem 24

Lotto: Draw N different random numbers from the set 1..M.

(1 8) 3 -> [7 3 5]


Problem 25

Generate a random permutation of the elements of a list.

[1 2 3 4 5] -> [2 5 1 3 4]


To be continued...