Task 1: Minimum Index Sum

You are given two arrays of strings.  Write a script to find out all
common strings in the given two arrays with minimum index sum. If no
common strings are found returns an empty list.

Example 1

Input: @list1 = ("Perl", "Raku", "Love")
       @list2 = ("Raku", "Perl", "Hate")

Output: ("Perl", "Raku")

There are two common strings "Perl" and "Raku".
Index sum of "Perl": 0 + 1 = 1
Index sum of "Raku": 1 + 0 = 1

Example 2

Input: @list1 = ("A", "B", "C")
       @list2 = ("D", "E", "F")

Output: ()

No common string found, so no result.

Example 3

Input: @list1 = ("A", "B", "C")
       @list2 = ("C", "A", "B")

Output: ("A")

There are three common strings "A", "B" and "C".
Index sum of "A": 0 + 1 = 1
Index sum of "B": 1 + 2 = 3
Index sum of "C": 2 + 0 = 2

MY NOTES: very easy.  Identify whether any common strings exist: set
intersection.  Then calculate index sum of all common strings and choose
the minimum ones.  Trickiest thing to work out is how to input two lists
of strings - let's choose an arbitrary separator ':'..

GUEST LANGUAGE: As a bonus, I also had a go at translating ch-1.pl into C
(look in the C directory for that).


Task 2: Duplicate and Missing

You are given an array of integers in sequence with one missing and one
duplicate.  Write a script to find the duplicate and missing integer in
the given array. Return -1 if none found.  For the sake of this task,
let us assume the array contains no more than one duplicate and missing.

Example 1:

  Input: @nums = (1,2,2,4)
  Output: (2,3)

  Duplicate is 2 and Missing is 3.

Example 2:

  Input: @nums =  1,2,3,4
  Output: -1

  No duplicate and missing found.

Example 3:

  Input: @nums = (1,2,3,3)
  Output: (3,4)

  Duplicate is 3 and Missing is 4.

MY NOTES: also pretty easy - especially if the list of integers should (if it
were not for the one missing and one duplicated) form the sequence 1..N.
if so: the duplicate is the element where el[i] != i.
The missing is the sole member of set {1..N} - all el[i]

Let's generalise it slightly to B, B+1, .. B+N-1.  Then: find the element
where el[i] != el[0]+i, that is the duplicate, and the missing is the sole
member of {B..N+N-1} - all el[i]

GUEST LANGUAGE: As a bonus, I also had a go at translating ch-2.pl into C
(look in the C directory for that)