競プロ典型 90 問 / Q027

Q027.cs

using System;
using System.Collections.Generic;

class Q027
{
	static void Main()
	{
		var n = int.Parse(Console.ReadLine());

		var set = new HashSet<string>();
		for (int i = 1; i <= n; i++)
		{
			var s = Console.ReadLine();
			if (set.Add(s)) Console.WriteLine(i);
		}
	}
}

Q027L.cs

using System;
using System.Linq;

class Q027
{
	static void Main() => Console.WriteLine(string.Join("\n", Enumerable.Range(1, int.Parse(Console.ReadLine())).GroupBy(_ => Console.ReadLine()).Select(g => g.First())));
}

https://atcoder.jp/contests/typical90/submissions/23091428
https://atcoder.jp/contests/typical90/submissions/22511273