I found this kata very interesting, although much more challenging than other katas of th 5th kyu that I did. I don't know if this kata is underrated, or the other katas overrated.

Thanks! I thought the inputlist had to be valid as well.

That's spoiling part of the solution. Please don't... One needs to think, try, fail, try again, to solve a kata (and learn), not read the Discourse page.

They shouldn't be all valid, that's a list of words, it can contain invalid ones and you can't use them. See the 5th example.

It was very fun kata, it took me 2 whole days to find a solution but it defiantly was worth the satisfaction, Thanks for the fun ;)

Java:

The sampletest input dataset is not valid against the requirements:

    String[] alice = new String[]{"plat", "rend", "bear", "soar", "mare", "pare", "flap", "neat", "clan", "pore"};
    String[] bob = new String[]{"boar", "clap", "mere", "lend", "near", "peat", "pure", "more", "plan", "soap"};

The third word of bob ("mere") does not have 4 unique letters