题解 | 字符个数统计

using System.Collections.Generic;
using System;
public class Program {
    public static void Main() {
        string line;
        while ((line = System.Console.ReadLine ()) != null) { // 注意 while 处理多个 case
            HashSet<char> set = new HashSet<char>();
            foreach(char c in line){
                set.Add(c);
            }

            Console.WriteLine(set.Count);

        }
    }
}

用上HashSet这种去重集合，解决很快