// Exercise 1: word frequency with Dictionary + HashSet (easy)
//
// Implement:
//   - CountWords(text): split on whitespace and punctuation (use the
//     provided Separators array), lowercase each word, ignore empty
//     strings, and return a Dictionary<string,int> of word -> count.
//     Use TryGetValue (or GetValueOrDefault) — never index a missing key.
//   - UniqueInOrder(words): return a List<string> containing each word
//     the FIRST time it appears, preserving order. Use a HashSet<string>
//     for the "seen" check so the whole method is O(n), not O(n^2).
//
// Run with: dotnet run (inside a console project) or paste into a Main method.

using System;
using System.Collections.Generic;

class Program
{
    static readonly char[] Separators = { ' ', '\t', '\n', ',', '.', '!', '?', ';', ':' };

#pragma warning disable IDE0060
    static Dictionary<string, int> CountWords(string text)
    {
        // TODO: split, lowercase, count
        return new Dictionary<string, int>();
    }

    static List<string> UniqueInOrder(IEnumerable<string> words)
    {
        // TODO: HashSet<string> seen; add to result only when seen.Add(w) returns true
        return new List<string>();
    }
#pragma warning restore IDE0060

    static void Main()
    {
        int pass = 0, total = 0;

        var counts = CountWords("The cat. The dog! the END, end?");
        total++;
        if (counts.Count == 4 && counts["the"] == 3 && counts["end"] == 2 && counts["cat"] == 1 && counts["dog"] == 1)
        { Console.WriteLine("PASS: CountWords"); pass++; }
        else Console.WriteLine("FAIL: CountWords, got " + string.Join(", ", counts));

        total++;
        if (CountWords("   ").Count == 0) { Console.WriteLine("PASS: blank input"); pass++; }
        else Console.WriteLine("FAIL: blank input should give empty dictionary");

        var unique = UniqueInOrder(new[] { "b", "a", "b", "c", "a" });
        total++;
        if (string.Join(",", unique) == "b,a,c") { Console.WriteLine("PASS: UniqueInOrder"); pass++; }
        else Console.WriteLine("FAIL: UniqueInOrder, got " + string.Join(",", unique));

        Console.WriteLine($"--- {pass}/{total} checks passed ---");
    }
}