Discussion on: AoC Day 2: Inventory Management System

[roeekl]

Part 1: C# + LINQ = one-liner

return (input.Count(id => id.GroupBy(c => c).Any(group => group.Count() == 2)) *
                   input.Count(id => id.GroupBy(c => c).Any(group => group.Count() == 3)))

Part 2

for (int i = 0; i < input[0].Length; i++)
            {
                var commonIds = input.Select(id => id.Remove(i, 1)).GroupBy(id => id).FirstOrDefault(group => group.Count() > 1);
                if (commonIds != null)
                {
                    return commonIds.First();
                }
            }