Task 1: "Diff-K

You are given an array @N of positive integers (sorted) and another non
negative integer k.

Write a script to find if there exists 2 indices i and j such that A[i]
- A[j] = k and i != j.

It should print the pairs of indices, if any such pairs exist.

Example:

    @N = (2, 7, 9)
    $k = 2

Output : 2,1"

My notes: sounds entirely straightforward.


Task 2: "Path Sum

You are given a binary tree and a sum, write a script to find if the tree
has a path such that adding up all the values along the path equals the
given sum. Only complete paths (from root to leaf node) may be considered
for a sum.

Example

Given the below binary tree and sum = 22,

          5
         / \
        4   8
       /   / \
      11  13  9
     /  \      \
    7    2      1

For the given binary tree, the partial path sum 5 - 8 - 9 = 22 is not valid.

The script should return the path 5 - 4 - 11 - 2 whose sum is 22.
"

My notes: Obvious question: how to represent binary tree.  Let's go with..
a traditional Perl OO self-printing package inline in the main program.

Second question: we'll need to parse a binary tree from the command line,
so what text format do we want to represent a parsable binary tree on the command line?
After some thought, decided on (5,(4,(11,l7,l2),n),(8,l13,(9,n,1))) where
(N,L,R) represents a node with value N, left tree L and right tree R;
lN represents a leaf with value N
n represents nil

There's a lot more code for this task 2 than for many, I don't know if
there's some simpler way of doing it that I'm missing?  Perhaps there's
a more concrete way of representing a binary tree that supports path summing?