so-47261385

Solves the question asked here: https://stackoverflow.com/q/47261385

1. Input array contains set of arrays.
2. Each inner array contains unique elements.
3. Each inner array may have different length and different values.
4. Output array must contain exact same values.
5. Output inner array must have unique values on same key.
6. If there is no solution, wildcard ie.: null are allowed.
7. Wildcards can be duplicated on same key.
8. Solution should have as few wildcards as possible.
9. Algorithm should be able to handle array up to 30x30 in less than 180 s.

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The idea is to identify conflicting elements and swap them to a column where they are no longer a problem. For cases where this is not applicable a random selection is done. The code works recursive and thus there are edge-cases where it takes very long to complete.

An extreme edge-case is an input where all rows consist of exactly the same values.

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Usage:

<?php
$solver = new SwapSolver();
$solution = $solver->solve([
    ['A', 'B', 'C'],
    ['A', 'B', 'C'],
    ['A', 'B', 'C'],
]);

---

Some commands to try:

> php solve.php solve unique --size=30 --num=1
> php solve.php solve random --size=30 --num=1
> php solve.php solve equal --size=30 --num=1
> php solve.php solve fixed --num=22

When $a \ne 0$, there are two solutions to $(ax^2 + bx + c = 0)$ and they are $$ x = {-b \pm \sqrt{b^2-4ac} \over 2a} $$