Task 1: "Fibonacci Sum

You are given a positive integer $N.

Write a script to find out all possible combination of Fibonacci Numbers
required to get $N on addition.

You are NOT allowed to repeat a number. Print 0 if none found.

Example 1:

Input: $N = 6

Output:
    1 + 2 + 3 = 6
    1 + 5 = 6

Example 2:

Input: $N = 9

Output:
    1 + 8 = 9
    1 + 3 + 5 = 9
"

My notes: ok. pretty straightforward, especially after last weeks' first task.
Not quite so trivial to do efficiently, my solution generates a lot of
duplicate solutions (hence the dedup() function), and is very slow for large N.
(See also ch-1a.pl for a tabulation of number of Fibonacci sums for i=1..N)


Task 2: "Lonely X

You are given m x n character matrix consists of O and X only.

Write a script to count the total number of X surrounded by O only. Print
0 if none found.

Example 1:

Input: [ O O X ]
       [ X O O ]
       [ X O O ]

Output: 1 as there is only one X at the first row last column surrounded
by only O.

Example 2:

Input: [ O O X O ]
       [ X O O O ]
       [ X O O X ]
       [ O X O O ]

Output: 2

    a) First  X found at Row 1 Col 3.

    b) Second X found at Row 3 Col 4.
"

My notes: interesting question, sounds simple but perhaps not quite
as simple as it sounds.  Especially (obviously) "surrounded by only O"..
Note that I counted rows and columns from 0, not 1.  So the output I
generate for the second grid (file grid2) is:
"2 lonely Xs in grid: [0, 2],[2, 3]"