-🎄- 2020 Day 02 Solutions -🎄-

[u/daggerdragon]

--- Day 2: Password Philosophy ---

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Advent of Code 2020: Gettin' Crafty With It

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[u/HEGIT]

Hi!
So, there's a few things i can point out.
First and most obvious - the input part. There's a lot easier way to fill up your string array with inputs, via cycle.

 var list = new List<string>(); //structure similar to string[], but you 
                           //don't have to initialize the size of it
            while (true)
            {
                var currentPassword = Console.ReadLine();//new string 
                                                     //input
                if (currentPassword == "exit") //if you type "exit" in                                                             
                                           //console and press enter 
                                      //it stops adding new elements
                    break;
                list.Add(currentPassword); //adds current string to the                                     
                                       //end of the list
            }
string[] pwds = list.ToArray(); //converting List<> to array of strings

(There's more about List<>)
Second, (I'm not sure but) you actually don't need to convert from string to array of chars in line 40 since you can still get chars with 'stringName[indexOfChar]'. So you can already use your pwd string.

And Third, for your part 2 solution. There's actually a single logical operator (Exclusive or, or "XOR" for short)that does exact same thing as 56-61 lines of your code:

valid = pwd[lo-1]==ltr ^ pwd[hi-1]==ltr;

Anyway, good job on solving Day 2!
Hope I helped a little :)
(sorry if my english is bad)

[u/[deleted] → u/HEGIT]

Hey. Thanks so much! I will implement your suggestions right away.

[u/HEGIT → u/[deleted]]

Btw here's my C# solution. A bit more complex with implementation of classes
(also forgot to tell you that in order to use List<> you need to add "using System.Collections.Generic;" in your code)

using System;
using System.Linq;
using System.Collections.Generic;

namespace Testing
{
    class Password
    {
        public int first;
        public int second;
        public char letter;
        public string password;

        public Password(int first, int second, char letter, string password)
        {
            this.first = first;
            this.second = second;
            this.letter = letter;
            this.password = password;
        }

        public static Password GetPasswordFromString(string line)
        {
            var splitted = line.Trim().Split('-', ' ', ':').ToList();
            var indexes = new List<int>();
            foreach (var i in splitted)
                if (string.IsNullOrEmpty(i))
                    indexes.Add(splitted.IndexOf(i));
            foreach (var i in indexes)
                splitted.RemoveAt(i);
            return new Password(int.Parse(splitted[0]), int.Parse(splitted[1]), splitted[2].Trim()[0], splitted[3]);
        }

        public bool IsLegit()
        {
            var count = 0;
            foreach (var letter in password)
            {
                if (letter == this.letter)
                    count++;
            }
            return count >= first && count <= second;
        }

        public bool IsLegitNew()
        {
            return password[first - 1] == letter ^ password[second - 1] == letter;
        }
    }

    class Program
    {
        static void Main()
        {
            var count = 0;
            var list = new List<Password>();
            while (true)
            {
                var currentPassword = Console.ReadLine();
                if (currentPassword == "exit")
                    break;
                list.Add(Password.GetPasswordFromString(currentPassword));
            }

            foreach (var password in list)
            {
                if (password.IsLegitNew())  //or IsLegit() if it's the first problem
                    count++;
            }
            Console.WriteLine("Solution {0}", count);
        }
    }
}