Solutions by Lubos Kolouch.

# The Weekly Challenge - 339

## Task 1: Max Diff

### Description

Given an array of at least four integers, find two disjoint pairs whose product
difference is as large as possible. The difference for pairs (a, b) and (c, d)
is `(a * b) - (c * d)`, and we are interested in the maximum absolute value of
this difference across all pair selections.

### Solution

#### Perl (ch-1.pl)

Enumerates every combination of four numbers, evaluates the three possible
pairings, and keeps the maximum absolute difference between the resulting
products. Input validation ensures the list has at least four elements, with
unit tests covering the provided examples.

#### Python (ch-1.py)

Uses `itertools.combinations` to iterate through all quadruples of integers and
checks the three pairings of each quadruple. Tracks the maximum absolute
product difference. Type hints and `unittest` cases cover the supplied
scenarios.

### Examples

- Example 1: `[5, 9, 3, 4, 6]` → `42`
- Example 2: `[1, -2, 3, -4]` → `10`
- Example 3: `[-3, -1, -2, -4]` → `10`
- Example 4: `[10, 2, 0, 5, 1]` → `50`
- Example 5: `[7, 8, 9, 10, 10]` → `44`

## Task 2: Peak Point

### Description

Given a list of altitude gains, starting from altitude zero compute the running
sum and report the highest altitude reached at any step.

### Solution

#### Perl (ch-2.pl)

Processes the gains sequentially, maintaining the cumulative altitude and the
highest value encountered. Embedded tests verify the challenge examples.

#### Python (ch-2.py)

Updates the running altitude for each gain and retains the maximum altitude
seen. Includes type annotations and unit tests mirroring the provided cases.

### Examples

- Example 1: `[-5, 1, 5, -9, 2]` → `1`
- Example 2: `[10, 10, 10, -25]` → `30`
- Example 3: `[3, -4, 2, 5, -6, 1]` → `6`
- Example 4: `[-1, -2, -3, -4]` → `0`
- Example 5: `[-10, 15, 5]` → `10`

## Running the Code

### Perl

```bash
perl ch-1.pl
perl ch-2.pl
```

### Python

```bash
python3 ch-1.py
python3 ch-2.py
```